Quantum computers: How do they work and what will we use them for?
Quantum computers are set to revolutionize technology far beyond the capabilities of today's digital systems. While conventional computers work with bits, quantum computers use qubits to solve highly complex problems in record time. Despite ongoing development challenges, they offer enormous opportunities in sectors such as finance, chemistry, logistics, and cybersecurity. Thanks to its world-class research and strong industrial base, Switzerland is well-positioned to benefit from these groundbreaking innovations. Discover how quantum computing could transform your industry.
Quantum computers are set to revolutionize technology far beyond the capabilities of today's digital systems. While conventional computers work with bits, quantum computers use qubits to solve highly complex problems in record time. Despite ongoing development challenges, they offer enormous opportunities in sectors such as finance, chemistry, logistics, and cybersecurity.
Thanks to its world-class research and strong industrial base, Switzerland is well-positioned to benefit from these groundbreaking innovations. Discover how quantum computing could transform your industry.
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Quantum computers
How do they work and what will we use them for?
Our lives have been characterised by digital technology since the invention of the semiconductor microchip.
The world relies on billions of smartphones and PCs, electric cars and satellites. Quantum computers represent
a further step and are being worked on feverishly around the world. Given the major expectations and unanswered
questions involved, it is worth getting to know quantum computers and their amazing functionality
and astonishing advantages, but also their disadvantages.
Spectacular 2nd quantum revolution
Firstly, what do widely used microchips have to do with the still little
known quantum computers? Microchips utilise a number of quantummechanical
phenomena from the so-called 1st quantum revolution
(also known as “Quantum 1.0”, see glossary). However, what we call
a quantum computer only became possible with the 2nd quantum
revolution (or “Quantum 2.0”). New insights into quantum physics
and ongoing technical progress made its realisation possible.
The expected characteristics mean the new quantum computer
generation will be able to solve extremely complex problems in the
future. There is no shortage of positive prophecies, especially for
industries such as chemistry, materials science, finance, logistics and
meteorology. The area of cybersecurity may also be strongly affected
by this development and will most probably experience massive
further development. Traditional network components are already
being upgraded to make them “quantum-safe”, meaning they are
protected against the decryption of certain security codes by quantum
computers.
High hopes and (even) greater hurdles
Are these new types of computers a disruptive innovation, and will
all computers soon be calculating with quanta? What can be said
now is that quantum computers will not replace our everyday digital
devices in the foreseeable future, but will complement them for
certain tasks. They will certainly be superior to today’s computers
when it comes to solving special problems of enormous computational
intensity.
An example is the area of encryption technology. RSA encryption,
which is considered the global standard and is based on the factorisation
of prime numbers, can be cracked within hours, if not minutes,
using a quantum computer, but conventional computers
would take years or decades. That is why work is already underway
on “post-quantum cryptography”. It comes as no surprise that the
quantum computer is seen as “the next really big thing” in tech and
investment communities. It is sometimes claimed it could change
“everything”– a typical indication of hype.
Demystification and orientation
Quantum computers could indeed fundamentally change our world.
As soon as stable, available and economically viable systems are developed,
they are likely to become pioneering instruments in various
branches of industry, research areas and economic sectors. The question
is only when and how the quantum computer disruption or, at
the very least, transformation will occur. And what the technology
will really be capable of once the fog of speculation has lifted.
No universally applicable quantum computer currently exists that
would be superior to conventional high-performance computers.
Conversely, we know of tested and proven “simpler” quantum 2.0
applications such as quantum measurement technology. It impresses
with its accuracy, as this surpasses previous methods by several
orders of magnitude. However, it will take some years before the
quantum computer becomes part of everyday life.
Contents
High-tech revolution with new physics 2
Quantum phenomena 3
What are quantum computers capable of? 5
Quantum computer technologies “in competition” 6
Advantages and disadvantages 7
Switzerland, a quantum computing hub 10
Most promising applications 11
Amazing (quantum) computer history 14
High-tech revolution with new physics
Of all the new quantum technologies of the 2nd quantum revolution,
quantum computing is regarded as a cutting-edge discipline.
One needs to solve so many physical, technological and programming
problems that, despite enormous international efforts, it will
take some years before practical and efficient quantum computer
products can be expected. On the other hand, quantum computing
also embodies enormous potential which could profoundly
change certain areas of the economy and society.
Weighting and forecasting of different quantum technologies.
Quantum
computing
Difficulty / Complexity / Business potential
Quantum
sensing
Quantum
key
exchange
Quantum
communication
Quantum
imaging
Quantum
widgets/apps
Quantum
networks
Quantum
games
2020 2025 2030 2035 2040 2045
Source: QIDIS (Quantum Industry Day in Switzerland) 2021 / P. Seitz
Quantum technologies of the 2nd quantum
revolution
Products that make practical use of the insights of the 2nd quantum
revolution are already being manufactured, both worldwide and in
Switzerland:
– Quantum key exchange, quantum sensing technology and
quantum imaging: Findings from these first “fruits” of quantum
technology can already be exploited for practical applications and
further research.
– Quantum networks and communication: In just a few years,
functional, reliable quantum communication networks should be
possible. For physical reasons, the latter will be absolutely tapproof,
thanks to quantum technology (secure by physics). Experts
estimate that commercial communication channels with quantum
cryptography could appear in around five years. A secure quantum
internet, on the other hand, could still take until 2050.
– Quantum widgets and games: Humans have always been extremely
inventive in their use of new technologies, and unexpected
applications have sometimes found widespread use and
been greatly beneficial. We are, as yet, unfamiliar with “quantum
widgets” and “quantum games”, but it is possible that
some clever mind will soon surprise us with them.
– Quantum computers: These are, in a sense, the ultimate application
of quantum technology, as they will one day solve
problems that cannot be solved with conventional computer
hardware in a reasonable amount of time.
Global quantum computer race
Despite many unanswered questions and enormously expensive
technology, the race to utilise the advantages of quantum computers
efficiently is well underway. There is, after all, a lot at stake, as
the great potential of quantum computing ranges from scientific
and technological applications to economic progress.
“Quantum information science is a
completely new way of harnessing
nature. It will be the first technology
that allows useful tasks
to be performed in collaboration
between parallel universes.”
David Deutsch,
Dirac and Isaac Newton Medal Laureate
2
Quantum computer | 2024
Worldwide public sector investment in quantum technologies in USD million
Denmark
406
European Quantum Flagship
1100
Sweden
160
Russia
1450
The Netherlands
1000
Finland
27
China
15,000
Canada
1100
US National
Quantum Initiative
3750
Brazil
12
United Kingdom
4300
France
2200
Spain
67
Switzerland
900
Germany
3300
Austria
127
Hungary
11
Israel
390
Qatar
10
South Africa
3
India
735
Thailand
6
Singapore
138
South Korea
2350
Japan
700
Taiwan
282
Philippines
17
Australia
599
New Zealand
37
Source: “Overview of Quantum Initiatives Worldwide 2023”, QURECA, 19 July 2023. Department of Industry, Science and Resources, Austria; ETH Domain (ETH Zurich, EPFL, PSI).
The diagram illustrates global investment in
quantum technology in 2023, whereby quantum
computing is considered the main application
of quantum technologies (reliable figures solely
relating to the area of quantum computing are,
unfortunately, not available). By comparison,
China spends around USD 15 billion annually
on this, and Switzerland USD 900 million.
While most nations and companies focus on
one or a few types of implementations (see
Chapter 4), partly for reasons relating to
resources, those that make large investments
usually pursue several approaches at the same
time to achieve progress and results as quickly
as possible.
Quantum phenomena
With their semiconductor structures of only a few nanometres, the
best of conventional microprocessors today soon reach their physical
limitations. The well-known Moore’s law (which is, strictly speaking,
not a law, but a self-fulfilling prophecy that has so far proved
accurate) by Intel co-founder Gordon Moore states that the number
of transistors on an integrated circuit doubles on average every two
years because of the efforts of research and industry.
This constant miniaturisation will eventually end on the atomic level.
In the smallest dimensions of our universe, the laws of classical mechanics,
as formulated by Isaac Newton, tend to fail. In systems consisting
of nanoscale particles such as photons and electrons, the laws
of quantummechanics prevail, which often contradicts our perception
of every day laws.
Plenty of room at the bottom
Paradoxically, where it becomes smaller and smaller by our usual
standards, a huge world opens up – the world of quanta. “There’s
Plenty of Room at the Bottom” is the title of a visionary lecture
given by physicist and Nobel Prize winner Richard Feynman in 1959.
In this lecture, he presented his ideas on how technology could
work at a sub-microscopic level – or even further “down” in the no
longer visible, nanoscale world. Only gradually do we discover how
the world is structured at the smallest dimensional level of atoms
(see glossary).
How can you imagine these incredibly small particles? Depending
on the element, atoms are only about 1–5 tenths of a nanometre
in size. A nanometre is one billionth of a metre. A grain of dust
contains around 100 million billion atoms – more than there are
stars in the universe. Today’s microelectronics, semiconductor
technology and optoelectronics with their LEDs, laser diodes and
displays are based on the “Quantum 1.0” class, where the simpler
phenomena of quantum physics, such as the quantisation of energy
states, the existence of pure energy packets (photons) and the interaction
of electrons with these photons – also known as QED
(quantum electrodynamics) – are used.
The new quantum technologies of the “Quantum 2.0” class utilise
the physical phenomena and processes of quantum mechanics at
the atomic and subatomic level. They utilise three additional quantum
phenomena: superposition (superposition of base states, whereby
measurement results can only be predicted by probabilities), entanglement
(whereby all components of entangled systems “know
about each other”) and interference (the possibility of manipulating
quantum systems in such a way that “disturbing” states are subtracted).
3
Three prerequisites for quantum computing
Superposition
The bit, the smallest unit of a conventional digital
computer, can only assume two states – either 0 or 1
– and arithmetic operations are usually performed
sequentially. Unless the computer has cores that
work in parallel. A quantum bit (qubit) in a quantum
computer, on the other hand, is in a state of superposition
of – usually two – base states during the calculation. The “calculation”
in a quantum computer is performed by systematically manipulating the
probabilities that the qubits are in certain base states. The result of a quantum
calculation is obtained by reading out the qubits, whereby these are
found with a certain probability in one of the base states. This is also the
reason why a quantum computer cannot deliver “perfect” results, but only
“probabilities”. The more often you repeat a quantum calculation, the more
accurate the result will be.
The physical properties of a quantum unit therefore remain undefined until
they are measured. Nobody knows what value a qubit “really” has, not even
the universe. Albert Einstein felt very uncomfortable with the idea that physics
is determined by chance when he said: “God does not play dice.” And yet
today we know that this is the case. In a quantum physical system, there is
no certainty (before the measurement) as to where a quantum particle is or
what state it is in – there are only probabilities. You cannot know more
about a particle than these probabilities.
Our everyday experience is based on the assumption that all objects have a
well-defined state, always and everywhere. But this is precisely not the case
for quantum objects. This behaviour is sometimes explained by the fact that
quantum objects are in different base states at the same time, a condition
known as the superposition principle. But this description is only a “visualisation
aid” for the identity of quantum objects, which can only be described
correctly with mathematical probabilities. That’s why it is so difficult, indeed
almost impossible, to visualise this behaviour.
Entanglement
The physicists’ second insight,
which explains the enormous potential
of quantum computers, lies
in understanding another strange
quantum physical phenomenon,
namely that quantum objects can
be connected/entangled in such a way that they influence
each other, even over long distances. As soon as
the value of one quantum object is identified through
measurement, the value of its entangled twin is also
clear, and that means immediately, even before it is
measured. If you change the quantum state of one
qubit, all the other entangled qubits also “feel” this
change and their quantum state changes accordingly.
In a classical computer, the bits are stored and processed
independently of each other. This is not the case with a
quantum computer. Each calculation step always affects
all entangled qubits and, therefore, the entire quantum
computer. The number of variables that can be used for
calculations in a classical computer thus increases linearly
with the number of bits. In a quantum computer, on the
other hand, the number of information units that can be
stored and processed increases exponentially with the
number of qubits.
The surprising effect of the “entanglement” of quantum
systems, even across astronomical distances, was another
source of suspicion for Albert Einstein throughout his
life. He called it “spooky action at a distance”. The definitive
proof of quantum entanglement, which is now recognised
as the central property of quantum computers,
was only demonstrated experimentally in 2015, resulting
in the Nobel Prize being awarded in 2022 to Alain Aspect,
John Clauser and Anton Zeilinger.
Interference
Quantum mechanical interference is the
consequence of the fact that the behaviour
of a quantum system is described by combining
all possible processes of the development
of the quantum system. However, this
“combination” is not achieved by simply
adding the final states. Instead, it must be taken into account that
quantum states are represented by wave functions. For this reason,
the amplitudes of all the wave functions involved must be added
together for the correct combination – in the same manner as with
water waves, for example. This makes it possible for different wave
contributions to cancel each other out for a final result. This means
that quantum particles are not found at certain locations or in final
states where they would be expected in classical physics. This mutual
cancellation of wave functions is a central tool in the programming
of quantum computers, because the aim of every efficient
quantum computer algorithm is to make the probability distribution
of final results as narrow as possible, thus obtaining as high a statistical
significance of the results obtained as practically feasible.
4
Quantum computer | 2024
What are quantum computers capable of?
Surprisingly, a definitive answer does not yet seem to exist to this
simple and obvious question. Mathematical complexity theory
deals with precisely such central questions. What is the “complexity”
of a problem, meaning how does the effort required to solve
a problem increase when the number of parameters (the problem
size) is increased? Good-natured problems show an increase in
effort that rises with a potency (e.g. quadratic) with the size of the
problem. Such problems can be solved with classical computers in
a reasonable amount of time.
Unfortunately, many important problems exhibit exponential complexity
behaviour. The computational effort increases exponentially
with the size of the problem, and soon a limit is reached where even
the fastest classical computer needs far too much time to solve a
problem. Such practical problems include the factorisation of numbers
(which is used for conventional encryption), the packing problem
(how can one pack the maximum number of objects of different
dimensions into a prescribed volume), the travelling salesman
problem (how can one traverse a route which must pass through a
given number of locations in a minimum amount of time – compare
with use case 2) or the simulation of quantum systems (especially of
molecules and their interactions with other molecules).
Computing capacity still undefined
Although complexity mathematicians are aware of their responsibility
to finally bring order to the world of complexity, they have
not yet succeeded in precisely defining the limits of the computing
power of quantum computers. All we know today is that both the
factorisation problem and the quantum system simulation with
quantum computers do not increase exponentially with the size of
the problem, but only to the power of one. However, for the most
important optimisation problems, it is still unclear whether the
computing effort of quantum computers increases exponentially
with the size of the problem, as is the case for classical computers.
The adjacent graphic illustrates the complexity map of computational
problems assumed by most complexity theorists today. The
PSPACE (polynomial space) shown consists of the set of calculation
problems for which the memory requirement with conventional
computers does not increase exponentially (i.e. with a polynomial).
The NP area (non-deterministic polynomial time)
comprises the calculation problems whose solution can be checked
with conventional computers with polynomial effort. P describes
the subclass of NP problems that can also be solved with polynomial
effort using conventional computers. A particularly important
class are the problems that are labelled NP-complete. It was mathematically
proven that finding a single polynomial solution for one
of the NP-complete problems would also work for all others. However,
it is assumed that conventional computers would have to
expend exponential effort to solve this class of problem.
PSPACE
NPcomplete
P
BQP
NP
Illustration of the
probable complexity
map of computational
problems. By Scott
Aaronson, The Limits
of Quantum, Scientific
American, 2008
And what about the capabilities of quantum computers? This capability
is described by the BQP class (bounded-error quantum
polynomial time), which includes all problems that can be solved
by a quantum computer in polynomial time. If the BQP class were
also to include the eminently important NP-complete problems,
this could expand the possible applications of quantum computers
enormously and endow the technology with significant practical
importance. But complexity theory has still not been able to prove
this. Rather, it is assumed that the NP-complete problems are outside
the BQP class and that the practical significance of quantum
computers therefore remains limited. This uncertain situation is illustrated
by the cloudy boundary in the chart.
“In AI, practice is wildly ahead of theory, and there’s a race for
scientific understanding to catch up to where we’ve gotten via
the pure scaling of neural nets and the compute and data used to
train them. In quantum computing, it’s just the opposite: there’s
right now a race for practice to catch up to where theory has
been since the mid-1990s.”
Scott Aaronson, Quantum Computing: Between Hope and Hype, 2024
5
Quantum computer technologies “in competition”
There are currently around 15 approaches worldwide, some of which are completely different, to help quantum computing achieve a
breakthrough. All these systems are based on the phenomena of superposition and entanglement of qubits, and each of them has advantages
and shortcomings.
Superconducting circuits
One of the most widespread types are superconducting qubits. These consist of
superconducting microwave oscillating circuits with a frequency in the range between 4
and 8 GHz. They are cooled as low as possible down to a few millikelvin above the
(unattainable) absolute zero temperature. These qubits can be easily manipulated by
microwave pulses and lose practically no energy, as the current flows without resistance
(superconductivity).
The extreme cold stabilises the sensitive quantum states
in the qubits by greatly reducing thermal noise.
This method is characterised by the “chandelier” refrigerator (mixed cryostat), cooled
and electrically connected with countless fine cables (see cover image). The computing
unit with the qubits is located at the bottom and therefore in the coldest part, and is
encased in multiple insulating layers. IBM, Google, IQM and Rigetti, among others, rely
on this type of quantum computer.
Ion traps
In this type of quantum computer, atoms or molecules are captured and
manipulated, often in a vacuum, by electromagnetic fields and lasers in
order to process and store information. They are suitable for precision
measurements and applications that require great stability and control.
Players in this field include IonQ, AQT, Infineon, Oxford Ionics, Universal
Quantum, Quantinuum and eleQtron.
6
Neutral (cold) atoms
In quantum computers with neutral atoms, these are often
“captured” contact-free in an ultra-high vacuum with the help
of many focussed laser beams, the so-called optical tweezers.
These quantum computers are less sensitive to stray electric
fields, making them suitable for quantum processors. Pasqal,
Atom Computing, ColdQuanta, Planqc and QuEra are exponents
of this approach. Photo: An arrangement of many neutral
caesium atoms confined in a grid of optical traps formed by
laser light.
Photonic quantum computers
Photons (light particles) are used to store, transmit and process quantum
information in this design. For large-scale quantum computers, photonic
qubits are a promising alternative to quantum computers based on
trapped ions or neutral atoms which require cryogenic or laser-generated
cooling. However, these quantum computers have to use photons “in
flight”, and their programmability is therefore limited compared to other
architectures.
Companies such as PsiQuantum, Quantum Computing Inc, ORCA
Computing and Xanadu are active in this area, although their technical
approaches differ greatly.
Alternatives for the construction of a functional quantum
computer are electrons on helium, diamonds with
integrated nitrogen atom defects (NV diamond) and
the topological approach from Microsoft.
Quantum dots (QD)
Quantum dots are artificial atoms made of
semiconductor material where the potential for the
charge carriers is not defined by the atomic nucleus,
but by voltages on the metal electrodes on the
semiconductor surface. In most cases, the QD qubit
is then defined by two magnetic spin states which
are manipulated by different applications of spin
resonance.
The companies involved here include Diraq,
Siquance and Quantum Motion.
Illustrations: Adobe Stock Photo | Infineon Technologies | Preston Huft, Saffman Lab | Adobe Stock Photo | Adobe Stock Photo
Quantum computer | 2024
Utilisation of various physical effects for the implementation of qubits
Natural Qubits
Synthetic/Artificial Qubits
Trapped Ions Neutral Atoms Photonics Superconducting
Qubits
Silicon
Quantum Dots
Topological
Qubits
Nitrogen
Imperfections
in Artificial
Diamonds
Qubit
coherence
time (sec.)
>1,000 1 ––––––––––––––––––– 0.00005 0.03 N/A N/A
Fidelity 99.9% 97% ––––––––––––––––––– 99.4% ~99% N/A 99.2%
No.
connected
qubits
High
Very high, low
individual control
––––––––––––––––––– High Very Low N/A Low
Companies
IonQ, Quantinuum
(formerly
Honeywell)
Infleqtion
(formerly
ColdQuanta),
QuEra Computing,
Atom Computing,
Q-Block
Computing Inc.
PsiQuantum,
Xanadu, QC82,
Quantum
Computing Inc.
(QCI)
Google, IBM,
Quantum Circuits
(QCI), Rigetti and
many more
HRL, Intel, SQC
Microsoft,
Bell Labs
Quantum
Brilliance, Xeedq,
SaXonQ
Advantages
– Very stable
– Highest achieved
gate fidelities
Many qubits 2D,
possibly 3D
– Linear optical
gates
– Integrated on
chip
Can represent
physical circuits on
chip
Borrows from
existing
semiconductor
industry
Greatly reduced
errors
Can operate at
room temperature
Disadvantages
– Slow sequence
– Many lasers are
needed
– Hard to program
and control
individual qubits
– Prone to failure
– Each program
requires its own
chip with unique
optical channels.
– No memory
– Must be cooled
to near absolute
zero.
– High variability in
fabrication
– Very sensitive to
disruptive factors
– Only a few
connected.
– Must be cooled
to near absolute
zero.
– High variability in
fabrication
Existence not yet
confirmed
– Difficult to create
high number of
qubits – Limited
computing
capacity
Source: Science / Chris Monroe. With permission from Klea Dhimitri, Hamamatsu Photonics USA
Advantages and disadvantages
There is no doubt that quantum computers are capable of performing
important computational and optimisation tasks in a reasonable
amount of time. However, enormous efforts must still be made for
the development of hardware and software solutions if quantum
computers are actually to become suitable for everyday use and
can be applied by numerous programmers to solve their problems
efficiently.
A number of quantum computer applications already exist; some
are exploratory, others are demonstrative in character. In most cases,
these are problems that conventional computers can only solve
with a great deal of computing capacity or by using approximation
methods. Thanks to the further development of classic algorithms,
conventional computers still lead the way.
This is because the usefulness of today’s quantum systems is limited
by the occurrence of errors. In order to maintain the fragile state of a
completely entangled quantum system with hundreds or thousands
of qubits, a quantum computer must in practice always be errorcorrected
again after a few dozen calculation steps, or the executed
programs are limited to a few hundred sequential operations.
Intensive research is also being currently conducted into eliminating
the errors that occur during operation for a commercially viable
quantum computer through integrated continuous error correction.
Alternative approaches attempt to achieve the necessary quality of
results through post-processing. If the quantum processors used for
computing can be further improved and scaled up, quantum computers
will be more efficient than conventional supercomputers in
just a few years’ time when it comes to solving significant problems.
7
Finding the needle in the haystack
Quantum computers are particularly suitable for solving complex problems in a defined area. They will probably be
able to crack the encryption protocols most commonly used today (based on the time needed for the factorisation
of prime numbers) within a few hours or minutes. This is because complexity mathematics has proved that the factorisation
of large numbers with quantum computers does not increase exponentially with the size of the number.
Cracking encryption protocols will probably not be a task that every home computer will have to master. However,
there is a growing market for IT security companies, governments, secret services and other circles. The problem
of insufficiently secure encryption protocols has been recognised, and quantum-safe encryption is being successfully
developed on a global level.
Simulate nature!
The physicist Richard Feynman expressed it memorably in 1981:
Nature does not behave according to “classical” physics. Anybody
wishing to simulate (the smallest particles in) nature
should adopt a quantum mechanical approach. This was the
starting signal for quantum computing.
“Nature isn’t classical, dammit,
and if you want to make a
simulation of nature, you’d better
make it quantum mechanical.”
Richard Feynman (1918–1988), Nobel Laureate, was referring
to classical, Newtonian physics, which is unable to describe
quantum mechanical processes in nature.
The simulation of the quantum systems of nature
through another, more controllable quantum system
– the quantum computer – has proved to be extremely
difficult. However, enormous progress in
the isolation, manipulation and recognition of individual
quantum objects, especially in the last decade,
indicates that these physical implementations of
“quantum simulators” have become a reality – albeit
not yet a marketable reality.
Many experts expect that these applications of quantum
computing technology in particular will have a
lasting impact on life sciences. If the properties of
large molecules and their interaction with their chemical
environment can be calculated efficiently, then
“computational chemistry” will soon become part of
everyday life, even for molecules of great complexity.
Promising candidates for new drugs or new materials
can be determined on the computer and require
much less experimental effort. Interactions of new
drugs in the human body no longer need to be investigated
in countless clinical trials, as the “digital patient”
could be simulated with increasing reliability
using quantum computers.
8
An enormous effort
In order to restrict the freedom of particles, or solely their movement, they need to
be immobilised in as far as possible through extreme cooling. Liquid helium is
required for this purpose, and unfortunately helium cannot be extracted from air,
as it is so light that gravity cannot retain it in the Earth’s atmosphere. Helium is
the only noble gas separated as a component of natural gas, meaning helium is
primarily of fossil origin. It is therefore essential to work with closed-loop cooling
systems that enclose the helium used so well that it cannot escape from the
cooling circuit for years.
For even simpler quantum computers, it could also be desirable in the long term to
dispense which can be further miniaturised, extreme cooling with helium and for
systems to function at higher temperatures, perhaps even at room temperature.
Illustrations: Adobe Stock Photo | GL Archive / Alamy Stock Photo
Quantum computer | 2024
Fault tolerance and decoherence
However, a quantum computer has an unpleasant trait on account of its physical, probabilistic
properties. The calculation result is not a precise number, but a statistically distributed
answer. Therefore, the same calculation must be repeated many times and the final result
determined by statistical analysis, in the simplest case by averaging. For this reason, it is
clear from the outset that a quantum computer cannot be used for all computing problems.
For example, what use is the extremely rapid calculation of a large, complex spreadsheet
if the calculation results achieved are not precise?
The results produced by a quantum computer are therefore not precise numbers; rather, they
need to be complexly aggregated from the statistical results of many quantum calculations.
Furthermore, quantum entanglement can quickly become unbalanced if all qubits are no
longer perfectly entangled with each other. As a result, calculation errors can accumulate,
and the calculation result could be completely wrong. In addition, environmental disturbances
of various kinds can lead to the decoherence of the crucial phenomena of superpositioning
and entanglement. This is why quantum computer architectures must be implemented
in a fault-tolerant manner whenever possible. A logical qubit is represented by a
small armada of 10 to 20 physical qubits. These physical qubits can then be used to identify
and eliminate possible errors and inconsistencies in regular “consolidation operations”.
“Anyone who is not
confused by quantum
mechanics has not
really understood it.”
Niels Bohr (1885–1962),
Nobel Laureate
The input/output problem
Compared to classical computers, quantum
computers can be faster when it comes to
problems of great complexity concerning
relatively small amounts of data. Theoretically,
quantum computers far outperform
classical computers in terms of computing
speed, provided the computing effort in a
quantum computer for a particular problem
does not increase exponentially with the
size of the problem. However, the error corrections
required at short intervals, including
when saving a data record for a problem,
mean the quantum computer can only
input and output a limited data record (I/O).
In addition, the results depend heavily on
the suitability of the algorithms used. To
date, only a few basic quantum computer
algorithms exist that can solve important
problems efficiently. Accordingly, the initially
higher time expenditure required for the
quantum computer only pays off after a
certain period of time.
Experts therefore assume that quantum computers will primarily be suitable for “computationally
intensive, low-data” problems in the foreseeable future. When processing enormous
data sets, such as when training artificial intelligence, conventional supercomputer solutions
with huge numbers of specialised, parallel computing chips with a conventional architecture
are superior to quantum computing.
Comparison of classical computers and quantum computers:
Calculation time with increasing problem size
Time
Equilibrium time
Classical
computer
Problem size (N)
Parity size
Quantum
computer
For small-scale problems, a classical computer is unbeatable, because it calculates the
result precisely in a series of steps. However, if the problem grows substantially, it
suddenly needs exponentially more time for these many steps (see blue line). A quantum
computer, on the other hand, has a linear, flatly increasing performance curve. It
calculates parallel, but inaccurately, and needs to repeatedly correct errors. For a task
which we consider to be very easy, such as 2 + 2, it needs time, but the solution to a
major task does not take much longer. The quantum computer therefore has an advantage
when it comes to major problems. The two computers are equal where they have
the same time to solve a problem of size N (intersection point).
(Source: ETH Zurich, Microsoft, ACM / P. Seitz)
9
Switzerland, a quantum computing hub
The race to be at the forefront of quantum computing is getting
increasingly tougher. Switzerland has been an international pioneer
in this field for decades and has established a major network of
quantum research expertise. In May 2021, Switzerland withdrew
from the negotiations on bilateral agreements with the EU. As a
result, the European Commission decided to downgrade Switzerland
to a non-associated third country in Horizon Europe. Because
of the strategic importance of the EU’s major quantum programmes,
Swiss researchers are now excluded from participating in these programmes.
This weakens Switzerland as a centre of research in the
quantum field, because if we are no longer allowed to work directly
with the best in this field, we will only learn at a later stage about
the most promising new research approaches and disruptive breakthroughs.
Source: SWISSNEX, 2023
National Initiatives (Headquarters)
1 Swiss Quantum Initiative
2 NCCR SPIN
3 NCCR SwissMAP
University Centres and Research Hubs
1 The Quantum Center at ETH Zurich
2 The Basel Quantum Center and Swiss Nanoscience
Institute at the University of Basel
3 The Center for Quantum Science and
Engineering (QSE) at EPFL
4 The ETHZ-PSI Quantum Computing Hub
5 The Quantum Center at the University of Geneva
6 Swiss Federal Laboratories for Materials Science
and Technology (EMPA)
7 Università della Svizzera italiana (USI)
8 University of Applied Sciences and Arts Northwestern
Switzerland (FHNW)
9 Lucerne University of Applied Sciences and Arts
(HSLU)
Ecosystem Builders and Accelerators
1 Switzerland Innovation Park Basel
2 Switzerland Innovation Park Innovaare
3 Switzerland Innovation Park West EPFL
4 QuantumBasel
5 QAI Ventures
6 CERN
7 The Geneva Science and Diplomacy Anticipator
(GESDA)
8 Verve Ventures
Private Companies and Centres
1 IBM Research
2 ID Quantique
3 Basel Precision Instruments
4 Zurich Instruments
5 Qnami
6 Swiss Centre for Electronics and Microtechnology
(CSEM)
7 Swissphotonics
8 Miraex
9 QZabre
10 Ligentec
11 Enlightra
12 Terra Quantum
13 IonQ
Government
1 Swissnex HQ
Other
1 World Economic Forum (WEF)
It is almost impossible to portray the many dozens of players in the dynamic landscape of Swiss quantum technology. The map shows the most
important research and innovation centres for quantum technology, both public and private.
Nevertheless, Switzerland is well positioned to develop further as
one of the leading ecosystems for quantum technologies. Its
strengths lie in cooperation in a spirit of partnership, a long-term
commitment to research, world-class universities and cutting-edge
technology that has already produced top industrial products of
Swiss provenance. Last but not least, as the home of CERN, the
European Organisation for Nuclear Research, Switzerland has direct
access to basic research, enabling it to gain a deep understanding
of the structure of matter. New insights in the field of quantum
physics can also be expected.
Quantum computers are likely to be of great significance in Switzerland,
simply because added value created in this country largely
occurs in sectors that are predestined for the new quantum com-
puter calculations. Over 55% of Swiss exports are in the pharmaceutical
and chemical categories. Banks and insurance companies
are also very important, as tasks relating to optimisation, risk management
and the prevention of fraud are addressed here that can
be solved efficiently with quantum computers.
Take chemistry. If, for example, one wanted to calculate the chemical
properties of the caffeine molecule precisely, one would need 10 to
the power of 48 bits (1048 = an octillion, i.e. a 1 with 48 zeros), and
this is currently impossible with a conventional computer. Ideally, just
160 qubits are needed for this purpose with a quantum computer.
The fact that IBM, one of the leading manufacturers, has located part
of its basic quantum computer research in Switzerland speaks in favour
of the many positive factors that come together in Switzerland.
10
Quantum computer | 2024
Most promising applications
Quantum computing: A growing ecosystem and industrial applications
Pharmaceuticals, medicine:
– Discovery of new drugs
– Digital twins
– Precision medicine
Chemistry:
– New catalytic converters
– Energy optimisation
– Precision agriculture
Automation, logistics:
– Route planning
– Traffic optimisation
– Supply chain management
Financial industry:
– Portfolio/risk management
– Credit assessment
– Fraud prognosis
Source: McKinsey, Dec. 2021
Where can quantum computers really show their strengths? The assumption is quantum system simulation, optimisation tasks (e.g. resource/transport
planning) and risk assessments (e.g. banking and finance). Quantum computers will probably have the greatest significance
in the calculation of quantum processes themselves. Pharmaceutical and chemical products can probably be simulated precisely in
the foreseeable future and their therapeutic efficacy and probable side effects will reliably predicted.
How important is quantum technology in Switzerland?
Dr Andreas Fuhrer
Manager Superconducting Quantum Hardware
IBM Research Europe – Zurich
Illustrations: IBM Research Europe – Zurich | Adobe Stock Photo
“Quantum technology has been expedited by huge advances in
materials and (nano)-technology. Today, this enables us to control
the quantum properties of materials and components with
unprecedented accuracy. The high level of technological innovation,
which requires extremely clean, precise and reliable manufacturing
of components, and the likely revolutionary applications in the fields
of communications, finance, chemistry and process optimisation
make quantum technology a very attractive emerging market for
Swiss companies looking to strengthen their core competencies –
from start-ups to established SMEs and large global enterprises.”
11
Use case 1: Chemistry, biology, pharmacy
The development of drugs or vaccines usually takes years –
at present. Quantum computers together with AI could massively
shorten the key processes of synthesis and efficacy testing
by allowing the behaviour of molecules and chemical
reaction sequences to be simulated precisely and reducing
the time and effort required for chemical-biological
tests. This should make the development
of treatments and drugs speedier, more sustainable
and more precise. The development of novel
biological products from simulations of protein
folding could lead to a breakthrough, thanks to
quantum computing. The same applies in personalised
and precision medicine, where huge data sets of
genomes and therapy results could be combed through in a
short time to find the right approach.
In computer-aided drug design and molecular
modelling, even supercomputers can only deliver
relatively imprecise results. The quantum
computer could make years of laboratory testing
superfluous and greatly accelerate discoveries.
Developers also pin their hopes on the quantum computer for
the development of new medications from low-molecular
compounds. These have the advantage of being able to slip
through cell membranes and reach intercellular targets. The development
of more resilient crops, aggregate food or the
recycling of plastic waste by bacteria could also experience
a development boost with the aid of quantum computing. One
example is the extremely complex three-dimensional folding of
a protein to determine how and whether it can carry out its
functions in the body correctly. Predicting the spatial structure
(folding) of a protein on the basis of the amino acid sequence
is therefore akin to the holy grail of biochemistry today. Since
the quantum computer is effective in mapping other quantum
systems, it should be able to play to its strengths here.
12
“If you change the way
you look at things, the
things you look at change.”
Nobel Laureate Max Planck (1858–1947)
Illustrations: Wikipedia | Adobe Stock Photo
Quantum computer | 2024
Use case 2: Logistics, trade, production
A conventional computer searches for a route for a lorry from a starting point
to the destination (red needle). To achieve this, it drives along all possible
roads successively until it either finds a connection (image on right) or realises
that it has ended up in the wrong place (image on left).
Logistics today are globally intertwined and more
complex than ever. Quantum computers could make
an important contribution to enhancing efficiency
and, simultaneously, achieving energy-saving and climate
targets. Examples include the sustainable optimisation
of container ship and truck routes, the reduction
of return transports of empties, the
distribution, storage and preservation of fresh food or
bridging of the last delivery mile through the clever
use of transporters, bicycle messengers or drones. In a
similar way, goods and energy flows for production
processes (raw material extraction, agriculture, etc.)
could be optimised.
Quantum computers always have an advantage
when it comes to finding new ways and means to
deal with sudden interruptions or supply bottlenecks.
Compared to conventional computers,
the “turbo management” of such disruptions
is an easy task for the quantum computer,
working as it does with a lot of information
at the same time.
In contrast, the quantum computer calculates all routes simultaneously and finds the
right path at lightning speed.
“For a specific, but very important and practically relevant class of
combinatorial optimisation problems, quantum computers have
a fundamental advantage over classical computers.”
Jens Eisert and his team investigated the “travelling salesman’s problem” in 2024, namely visiting N reference points (cities etc.)
by the shortest route. As the number N increases, the computing time on a classical computer explodes (e.g. 10 cities: over 3.6 million
possible paths) – but this is not the case on a quantum computer.
13
Astonishing (quantum) computer history
The entanglement of
qubits is definitively
proven for the first time.
Alain Aspect, John F.
Clauser and Anton
Zeilinger receive the
Nobel Prize in Physics for
their work.
©TT News Agency /
Alamy Stock Photo
2022
D-Wave presents
the first commercial
quantum
computer with
128 qubits.
©Adobe Stock Photo
2011
The first
quantum
annealer
computer is
demonstrated.
2007
Establishment
of the Swiss
Quantum
Initiative SQI.
2023
Google claims to have
achieved the first “quantum
superiority” with its
Sycamore chip. However, the
fact that its quantum
computer is faster than any
conventional computer is
only true for a very specific
problem.
©Adobe Stock Photo
2019
IBM launches
“Quantum
Computing
as a Service”
(cloud access).
2016
The first 12-qubit
quantum computer
is developed
by researchers
from Canada and
the United States.
2006
William Shockley, John
Bardeen and Walter Brattain
invent the transistor. It is the basis
of modern microelectronics and
the digitalisation of our world.
©Wikipedia | Benedikt Seidl
1947
1964
©CERN
John Stewart Bell’s inequality states that
it is never violated in classical physics – but
it is in systems with quantum entanglement.
This theoretically refuted Einstein’s
conviction that “God does not play dice!”
(i.e. physics knows no coincidences or
probabilities). The Nobel Prize winners of
2022 provided the evidence.
©Wikipedia
Hertha Sponer makes extensive
contributions to the
application of quantum
theoretical methods in atomic
and molecular physics.
Together with Hedwig Kohn,
she confirms a number of
quantum mechanical
predictions in experiments.
1960
©Wikipedia
Erich Hückl formulates the fundamentals
of quantum chemistry.
Alexander Holevo proves
that n qubits can store
more information than n
classical bits.
1973
1940
©UtCon Collection /
Alamy Stock Photo
Erwin Schrödinger
formulates a quantum
mechanical wave equation
to calculate the probability
distribution for the
transport of quantum particles
and their possible
energetic states.
Werner Heisenberg, Max
Born and Pascual Jordan
publish the first conceptually
autonomous and logically
consistent formulation of
quantum mechanics based
on matrix calculations.
©Pictorial Press Ltd /
Alamy Stock Foto
1925
Albert Einstein, Boris Podolsky and Nathan
Rosen solve the EPR paradox named after
them. In theory, it should be possible to
perform a “measurement” on a particle without
disturbing it directly by performing this
measurement on a distant, entangled particle.
This fact could only be proven around 90 years
later.
©Adobe Stock Photo
1935
Albert Einstein describes
the photon and the photo
effect. His revolutionary light
quantum hypothesis states
that light consists of portions
(quanta) of energy. He is
awarded the Nobel Prize in
Physics in 1921 for this.
14
Quantum computer | 2024
The first five-photon
entanglement is
demonstrated by
Jian-Wei Pan.
©Uuongkinghe
2004
The race for
functional
quantum computers
First ion trap quantum
computer, first idea of
the adiabatic quantum
computer.
2000
© Infineon Technologies
1996
Lov Grover reveals the
first quantum search
algorithm. David
DiVincenzo defines the
criteria for a quantum
computer. Seth Lloyd
presents an algorithm that
can simulate quantum
mechanical systems.
Emanuel Knill,
Raymond Laflamme
and Gerard Milburn
establish linear
optical quantum
computing.
©BBC Bitesize
1
15
3
5
Lieven Vandersypen
and Matthias Steffen
publish the first
quantum computing
implementation of
Shor’s algorithm by
splitting the number
15 into its prime
numbers 3 and 5.
2001
Development of
quantum algorithms
©International Centre
for Theoretical Physics
1994/95
1981
Quantum computing in the lab
Richard Feynman proposes that
quantum phenomena be calculated
with a computer that uses/manipulates
individual quantum states and suggests
how a quantum computer could work.
David Deutsch formulates
the idea of the universal
quantum computer and the
principles of quantum
computing algorithms. He is
therefore regarded by many
as the founder of quantum
computing.
1985
Peter Shor publishes an algorithm
with which a future quantum
computer should be able to factorise
large integers exponentially faster
and, consequently, be able to crack
common encryption techniques. He
also proposes the first schemes for
quantum error correction.
Together with Paul Benioff and
David Deutsch, Richard Feynman
attempts to combine quantum
mechanics and computer science.
This means using quantum
simulators to simulate certain
problems that cannot be
modelled with a classical
supercomputer.
©Justinhsb
1982
1992
Ben Schumacher develops the first qubits and
the first Q-dots at the turn of the millennium.
Theoretical principles of quantum computing
Max Planck formulates the
hypothesis that energy states are
quantised. In 1919, he is awarded the
Nobel Prize in Physics for establishing
the quantum theory.
©André de Saint-Paul
1900
Invention of binary data processing
In 1725, Basile Bouchon from Lyon works on a way to
make textile weaving easier. Using a perforated roll of
paper that scans his mechanism, he succeeds in programming
fabric patterns. This is further developed with the aid
of J.-M. Jacquard’s punched cards (still in use 300 years
later!) that make his mechanical loom successful.
18th century
©Wikipedia
1905
By 1890, Herman Hollerith’s
electromechanical tabulating
machines were already using
millions of punched cards as
processing memory for the
US census. This requires an
entire system of punching,
reading and sorting devices.
Around 1820, Charles Babbage
invented the Difference Engine
and, in 1837, the first universal
calculating machine, the
Analytical Engine, both purely
mechanically operated devices.
The noblewoman Ada
Lovelace is the first person to
write a computer program for
the Analytical Engine.
©Wikipedia
19th century
15
Abstract
Unlike conventional computers, quantum computers do not calculate with digitally coded bits (0 and 1), but with a
superposition of the quantum states of several quantum bits (qubits). These systems, which consist of interacting
(entangled) nanoscale particles such as photons and electrons, are governed by the laws of quantum mechanics.
Quantum computers therefore have the unprecedented potential to solve highly complex computing and optimisation
tasks at great speed, but still require considerable development work in hardware and software to make
them suitable for everyday use.
Current applications of quantum computers demonstrate that classical computers with optimised algorithms are
currently still more efficient, as the susceptibility to errors and instability of quantum computers limits their usefulness.
Major advances in materials and nanotechnology have significantly advanced quantum technology, enabling
ever more precise control of quantum properties.
The new technology promises novel, revolutionary application options. Excellent quantum research is being
conducted in Switzerland in universities, research institutions and start-ups. As some of the anticipated fields of
application for quantum computers – including communications, finance, chemistry, pharmaceuticals, logistics and
process optimisation – correlate with the established strengths of the Swiss industry and economy, our country
could benefit significantly from this development in the coming years.
The Swiss Academy of Engineering Sciences SATW is the most important network of experts for
engineering sciences in Switzerland and is in contact with the highest Swiss bodies for science, politics
and industry. The network is comprised of elected individual members, member organisations and
experts.
On behalf of the federation, SATW identifies industrially relevant technological developments and
informs politics and society about their importance and consequences. As a unique expert organisation
with high credibility, it conveys independent and objective information on technology – as the
basis for establishing well-founded opinions. SATW also promotes the interests and understanding of
technology in the population, including young people in particular. It is politically independent and
non-commercial.
Imprint
Authors: Prof. Peter Seitz, Caspar Türler
Editing: Translingua AG
Cover image: Adobe Stock Photo
Design: Andy Braun
Print: Egger Druck
December 2024
DOI: doi.org/10.5281/zenodo.14040194
Swiss Academy of Engineering Sciences (SATW)
St. Annagasse 18 | 8001 Zurich | 044 226 50 11 | info@satw.ch | www.satw.ch
Glossary
Absolute zero temperature
Absolute zero, meaning the physically lowest possible temperature, is around three degrees lower
than the temperature in space, namely minus 273.15 degrees Celsius or 0 degrees Kelvin. This lowest
temperature is achieved down to a few millionths of a degree in the laboratories of low-temperature
physicists. It is possible to generate temperatures of up to approximately 1 millikelvin with a helium
mixture (i.e. within approximately one thousandth of a degree Celsius of absolute zero) in the laboratory.
Atom
In the 5th century BC, the ancient philosopher Leucippus of Miletus and his pupil Democritus of
Abdera developed the concept that the world was made up of a number of tiny, indivisible particles
known as atoms (Greek: átomos, “the indivisible”). We recognise 118 atoms in the periodic system of
chemical elements today, along with the particles of which they consist: protons and neutrons that
form the core, and electrons that surround this core. Protons and neutrons are in turn composed of up
quarks and down quarks. With its cloud of electrons, the atom is around 100,000 times larger than its
nucleus. If the atomic nucleus were the size of an apple, the atom would have a diameter of around
10 kilometres. Although we perceive matter as solid, individual atoms are largely empty. Even a diamond
consists mainly of empty space!
Bit
A portmanteau of binary digit, the binary number has the value 1 or 0. It is the unit of measurement for
the amount of digitally represented data (stored, transmitted).
Quantum
Originating from the Latin quantus (how big? how much?), this is the smallest known unit of measurement.
A particle confined in a finite space can only assume a limited number of energy states, as the
energy of the particle is quantised. A quantum is therefore an object that is generated by a change of
state in a system with discrete (quantised) values of a physical quantity. Quantised quantities are described
within the framework of quantum mechanics and sub-areas of theoretical physics inspired by
this, such as quantum electrodynamics. For example, light of a fixed frequency delivers energy in the
form of quanta called “photons”. Each photon of this frequency has the same amount of energy, and
this energy cannot be broken down into smaller units. Every atom in the universe contains quanta.
The human body alone consists of around 7x10 to the power of 27 atoms, equivalent to 7 quadrillion
(or 7 billion billion billion) atoms.
Quantum revolution 1.0
Technologies based on the understanding of fundamental quantum mechanical effects, in particular
the quantisation of energy, the existence of pure energy packets (photons), the interaction of photons
and electrons, quantum tunnelling phenomena or spin. This allows valuable products such as transistors
and chips, semiconductor sensors, LEDs, laser diodes, photovoltaic cells and magnetic resonance
tomographs to be realised.
Quantum revolution 2.0
Technologies that utilise additional quantum phenomena, in particular
– superposition (the condition of a quantum object can only be described as probability distribution,
where different basic conditions are detected through measurement);
– interference (quantum states can be manipulated so that certain final states can be excluded, meaning
their probability is subtracted to a minimum);
– entanglement (where the components of an entangled quantum system are instantaneously
“aware” of each other, meaning the component measurement results are strictly correlated). Consequently,
products with enormously enhanced performance can be realised, including quantum computers,
absolutely tap-proof quantum communication networks, quantum sensors with a sensitivity
enhanced by several orders of magnitude or quantum microscopy.
Qubit: Quantum bit
A system of two states that can only be correctly described by quantum mechanics, and which has
only two states that can be reliably distinguished by measurement. The qubit plays a role analogous to
the classic bit in conventional computers. It serves as the smallest possible storage unit and, simultaneously,
defines a measure for quantum information. Today’s qubits have a size of between 10 to the
power of -3 metres (= 1 millimetre) and 10 to the power of -10 metres (= 0.1 nanometres or 1 ten
billionth of a metre).
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