Displaced Fock states and their connection to quasiprobabilities

We employ spin-dependent optical dipole forces to characterize the transverse center-of-mass (COM) motional mode of a two-dimensional Wigner crystal of hundreds of 9 Be + . By comparing the measured spin dephasing produced by the spin-dependent force with the predictions of a semiclassical dephasing model, we obtain absolute mode temperatures in excellent agreement with both the Doppler laser cooling limit and measurements obtained from a previously published technique (B. C. Sawyer et al. Phys. Rev. Lett. 108, 213003 (2012)). Furthermore, the structure of the dephasing histograms allows for discrimination between initial thermal and coherent states of motion. We also apply the techniques discussed here to measure, for the first time, the ambient heating rate of the COM mode of a 2D Coulomb crystal in a Penning trap. This measurement places an upper limit on the anomalous single-ion heating rate due to electric field noise from the trap electrode surfaces of dn dt ∼ 5 s −1 for our trap at a frequency of 795 kHz, wheren is the mean occupation of quantized COM motion in the axial harmonic well.

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“…The spin-dependent ODF then produces displaced Fock states, |α, n , as [50] |ψ 2 =D SD (α)|ψ 1 = 1 √ 2 (|↑ |α, n + |↓ | − α, n ) .…”

Section: Discussionmentioning

confidence: 99%

Spin dephasing as a probe of mode temperature, motional state distributions, and heating rates in a two-dimensional ion crystal

2014

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“…, and is peaked around n a = n b and zero everywhere else for small X [28]. Therefore we approximate…”

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confidence: 99%

Continuous joint measurement and entanglement of qubits in remote cavities

2015

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We present a first principles theoretical analysis of the entanglement of two superconducting qubits in spatially separated microwave cavities by a sequential (cascaded) probe of the two cavities with a coherent mode, that provides a full characterization of both the continuous measurement induced dynamics and the entanglement generation. We use the SLH formalism to derive the full quantum master equation for the coupled qubits and cavities system, within the rotating wave and dispersive approximations, and conditioned equations for the cavity fields. We then develop effective stochastic master equations for the dynamics of the qubit system in both a polaronic reference frame and a reduced representation within the laboratory frame. We compare simulations with and analyze tradeoffs between these two representations, including the onset of a non-Markovian regime for simulations in the reduced representation. We provide conditions for ensuring persistence of entanglement and show that using shaped pulses enables these conditions to be met at all times under general experimental conditions. The resulting entanglement is shown to be robust with respect to measurement imperfections and loss channels. We also study the effects of qubit driving and relaxation dynamics during a weak measurement, as a prelude to modeling measurement-based feedback control in this cascaded system.

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“…It is worth stressing the close similarity of these states, written as in Eq. (3.10), with the expansion for Fock-displaced states [41], although their arguments differ in the sign, which introduces remarkable differences in the photon-number distribution.…”

Section: B Intelligent Statesmentioning

confidence: 98%

Extremal states for photon number and quadratures as gauges for nonclassicality

et al. 2015

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Rotated quadratures carry the phase-dependent information of the electromagnetic field, so they are somehow conjugate to the photon number. We analyze this noncanonical pair, finding an exact uncertainty relation, as well as a couple of weaker inequalities obtained by relaxing some restrictions of the problem. We also find the intelligent states saturating that relation and complete their characterization by considering extra constraints on the second-order moments of the variables involved. Using these moments, we construct performance measures tailored to diagnose photon-added and Schrödinger-cat-like states, among others.

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Displaced Fock states and their connection to quasiprobabilities

Cited by 93 publications

References 13 publications

Spin dephasing as a probe of mode temperature, motional state distributions, and heating rates in a two-dimensional ion crystal

Spin dephasing as a probe of mode temperature, motional state distributions, and heating rates in a two-dimensional ion crystal

Continuous joint measurement and entanglement of qubits in remote cavities

Extremal states for photon number and quadratures as gauges for nonclassicality

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