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Qubit-Coupled Mechanics - IFSC

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The Dispersive Coupling Limit<br />

*See: Irish & Schwab, PRB 68, 155311 (2003)<br />

Interaction Leads to Shift in Energy of CPB and NEMS<br />

Analogous To dispersive shifts in CQED<br />

Two Dispersive Effects Occur<br />

CPB-state-dependent<br />

Frequency<br />

Shift in NR<br />

NR- dependent<br />

shift in CPB<br />

transition energy<br />

N ≡ # Quanta in NR<br />

χ = 2λ 2 /ΔE<br />

Analogous to single-atom<br />

refractive shift in CQED<br />

δω ± ≈ ±ħχ<br />

Analogous<br />

to Lamb Shift<br />

δE ≈ ħχ(2N + 1)<br />

Analogous<br />

to Stark Shift<br />

Energy levels w/o interaction<br />

N = 2<br />

N = 1<br />

N = 0<br />

…<br />

…<br />

…<br />

ħω 0<br />

∆E<br />

|−⟩ |+⟩<br />

Energy levels with interaction<br />

N = 2<br />

N = 1<br />

N = 0<br />

∆E + 3ħχ<br />

…<br />

∆E + ħχ<br />

|−⟩ |+⟩<br />

2<br />

1<br />

1<br />

0<br />

Dispersive interaction is non-destructive: H iii ∝ σ z ⋅ a † a ⇒ H 0 , H iii = 0

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