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puters to talk to each other. Usually IPC delivers quite a bit better performance, but a TCP network connection has two major advantages that far outweigh the performance impact in most cases. First, a TCP connection can transparently support different Modules running on different computers that are attached to the Internet from anywhere in the world if needed. This allows LabRAD to be trivially distributed to inherently address the Load-Sharing Requirement. It also provides other conveniences like fast remote access. Second, every major programming language has native support for TCP/IP connections available. This makes it possible to provide an interface to the LabRAD system from languages as diverse as Python, Delphi, LabVIEW, Java, Matlab, etc. The performance impact from using TCP over IPC is reduced significantly by the immediate availability of fast networking infrastructure up to 10 GBit/s. This performance is likely to increase even further in the future, making the choice very acceptable. In fact, for the current requirements in our lab, a dedicated 100 MBit connection is more than enough to not cause a noticeable performance impact, so the dedicated 1 GBit LAN that we are currently using will be able to deliver sufficient performance for quite some time. Furthermore, network latencies and bandwidth limitations can often be hidden entirely by things like pipelining. 134
7.3.3 Cross-Language and Cross-Platform Since every programming language has its unique strengths but certainly also its weaknesses, it is a major advantage to be able to write different Modules in different languages. For example, Modules that require the best possible performance should be written in a compiled language like Delphi or C++. Modules that rely on a comprehensive user interface can easily be designed in LabVIEW. And Modules that script complex processes can be quickly implemented in Python. The data-structures that LabRAD supports were specifically designed to make implementation in different languages as natural as possible and thus it is possible to provide very seamless interfaces to LabRAD for almost all programming languages. In this way, LabRAD addresses the Flexibility and the Integration Requirement in one shot. Furthermore, it is possible to design LabRAD Modules for different operating systems that can all communicate via the OS agnostic network protocol. This allows for further flexibility in the choice of resources used for the project. For example, employing computers running a free operating system like Linux can slightly reduce the overall cost of the project. 135
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UNIVERSITY of CALIFORNIA Santa Barb
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Benchmarking the Superconducting Jo
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viii
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Curriculum Vitæ Markus Ansmann Edu
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99:187006 Lisenfeld, J., Lukashenko
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Abstract Benchmarking the Supercond
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Contents Contents List of Figures L
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4.1.3 Readout Squid Parameters . .
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7.5.5 Grapher . . . . . . . . . . .
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11.5 Analysis and Verification . .
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List of Figures 2.1 Inductor-Capaci
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List of Tables 3.1 Transition Matri
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Chapter 1 Quantum Computation 1.1 M
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for such problems include factoring
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if present encrypted data will rema
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In terms of quantum bits, this mean
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1.2.3 Implications - The EPR Parado
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proposed architecture of quantum bi
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“coherence times”, i.e. the tim
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Chapter 2 Superconducting Josephson
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of the glue-circuitry needed to con
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Figure 2.1: Inductor-Capacitor Osci
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• The circuit needs to be cooled
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Figure 2.2: Josephson Tunnel Juncti
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the trace along the V-axis, gives c
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Figure 2.4: Josephson Qubits: Sligh
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the cosine forms a local minimum al
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Figure 2.5: Example Qubit Coupling
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Readout schemes can further be cate
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states in the qubit’s inductor, t
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at time t. r is not restricted to b
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3.1.2 Effects of a Time Dependent P
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In some cases, it is possible to so
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Figure 3.1: Examples of Numerical S
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• The energy difference between t
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like this: V = ( V (−1, −1), V
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Figure 3.2: Simulation of LC Oscill
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Table 3.1: Transition Matrix Elemen
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with ω mn = Em−En . Multiplying
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α, it can be ignored. Thus, the in
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e solved exactly: A(t + ∆t) = e
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qubits would be simulated using: A(
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This calculation assumes that the s
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Decoherence consists of two parts:
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Note the difference in signs of the
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Chapter 4 Designing the Phase Qubit
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mutual inductance between the qubit
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During the measurement, the | 1 〉
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the right impedance transformation
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excitations. Since these are a pote
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Figure 4.3: Squid I/V Traces - a) L
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Figure 4.5: Qubit Integrated Circui
Page 111 and 112: The geometry of the qubit junction
Page 113 and 114: squid loop. Thus, this tool can be
Page 115: now, amorphous silicon seems to pro
Page 118 and 119: Figure 5.1: L-Edit Mask Layout Tool
Page 120 and 121: Figure 5.2: Fabrication Building Bl
Page 122 and 123: Figure 5.3: Photolithography and Et
Page 124 and 125: times the removal can be a bit tric
Page 126 and 127: Figure 5.4: Clearing Vias from Nati
Page 128 and 129: 5.6 Junction Layers 5.6.1 Oxidation
Page 130 and 131: top wiring layer to protect all low
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Page 134 and 135: 6.1 Physical Quality Control during
Page 136 and 137: 6.1.3 Atomic Force Microscopy To re
Page 138 and 139: Figure 6.1: 4-Wire Measurement - a)
Page 140 and 141: 6.3 Quantum Measurements at 25 mK 6
Page 142 and 143: seems to be a box machined out of s
Page 144 and 145: Figure 6.2: Dilution Refrigerator W
Page 146 and 147: cessing data. This protects the vol
Page 148 and 149: 6.3.9 Anritsu Microwave Source The
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Page 152 and 153: ment, the scalability requirements,
Page 154 and 155: people without any formal training
Page 156 and 157: 7.2.4 Performance Last, but certain
Page 158 and 159: or a Client Module. Client Modules
Page 160 and 161: second Module talks to all these an
Page 164 and 165: 7.3.4 Performance Addressing the Pe
Page 166 and 167: is designed such that the LabRAD Ma
Page 168 and 169: Table 7.3: LabRAD Type Annotations
Page 170 and 171: listed in Table 7.3. For transmissi
Page 172 and 173: Architecture to manage network conn
Page 174 and 175: Manager. In fact, in our lab, the o
Page 176 and 177: waiting for their completion. The C
Page 178 and 179: mentation of pipelining and certain
Page 180 and 181: Since the API guarantees that all R
Page 182 and 183: one microwave line for X/Y-rotation
Page 184 and 185: 7.5.3 DC Rack Server The DC Rack Se
Page 186 and 187: data taking on the lab servers and
Page 188 and 189: keys and the ability to set Context
Page 190 and 191: a certain time. 7.5.9 Optimizer Cli
Page 192 and 193: ters read from different sub-direct
Page 194 and 195: efore the execution of the sequence
Page 196 and 197: can achieve very-close-to hardware
Page 198 and 199: type to provide a one-stop location
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Page 202 and 203: 8.1 Squid I/V Response As explained
Page 204 and 205: a digital signal via the use of a c
Page 206 and 207: energy landscape (see Chapter 2.2.3
Page 208 and 209: Figure 8.3: Squid Steps Failure Mod
Page 210 and 211: At this point, the squid ramp can b
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starts to tunnel to the neighboring
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Figure 8.5: General Bias Sequence -
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Figure 8.7: Spectroscopy - a) Bias
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Figure 8.8: Rabi Oscillation - a) B
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ensemble with respect to each other
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Figure 8.10: T 1 - a) Bias sequence
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Figure 8.11: Ramsey - a) Bias seque
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phase shift into the middle of the
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photon excitation behaves similarly
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is desirable to modularize the cont
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sequence was run. This allows for t
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possible to read out all qubits cor
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simultaneous application of such me
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Figure 9.4: Capacitive Coupling Swa
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Figure 9.6: Capacitive Coupling Pha
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a phase difference of 0 ◦ rather
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Figure 9.7: Fine Spectroscopy of Re
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Figure 9.8: Swapping Photon into Re
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esonator. The latter calibration is
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Figure 9.11: Resonator T 1 - a) Seq
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224
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He does not throw dice” [Einstein
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(independent of which axis it is),
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of E xy is measured by expressing i
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For a measurement of two particles
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10.2.1 Photons The first and most n
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10.2.3 Ion and Photon In the attemp
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238
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11.1 State Preparation Since the ab
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Figure 11.1: Bell State Preparation
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Table 11.1: Entangled State Density
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Figure 11.2: Bell Measurements - a)
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11.2.3 Statistical Analysis For the
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11.3 Calibration The most difficult
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Table 11.4: Sequence Parameters - R
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ally determine an optimal value for
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ages are based on this method, incl
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equires to converge. Since the algo
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Table 11.7: Bell Violation Results
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Table 11.9: Error Budget - Capaciti
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Bell inequality. To make this claim
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11.5.2 Dependence of S on Sequence
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point where the measurement happens
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The second qubit is not driven and
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Figure 11.6: Resonator Coupled Samp
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From the resulting states, the 16 p
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Table 11.14: Error Budget - Resonat
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sponding to a violation by 244.0σ.
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educe energy decay and dephasing an
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John F. Clauser, Michael A. Horne,
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J. Majer, J. M. Chow, J. M. Gambett
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Matthias Steffen, M. Ansmann, Rados
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