Multi-qubit joint measurements in circuit QED: stochastic master equation analysis

Criger, Ben; Ciani, Alessandro; DiVincenzo, David P.

doi:10.1140/epjqt/s40507-016-0044-6

Cited by 13 publications

(20 citation statements)

References 35 publications

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“…If we set χ 1 = χ 2 = χ and χ 12 = 0, the parity condition Eqs. (23) reduces to the one reported in [10,11]. However, we see the important role that the quantum switch coefficient χ 12 plays in these equations.…”

Section: B Parity Conditionmentioning

confidence: 49%

“…We also consider the case in which we are able to set χ 12 = 0. As in [11], we consider a realistic piecewise pulse The measured quadrature of the output field is always chosen to be the one that maximizes the information content about the state of the system. (b) Difference between information gain about the Hamming weight and parity on a log 10 scale.…”

Section: Information Gain In Dispersive Parity Measurementmentioning

confidence: 99%

“…We take equal photon decay rates for the two resonators κ 1 = κ 2 = κ, with κ/2π = 5 MHz and set also χ 1 = χ 2 = χ = −κ/2 [42]. In this way, we achieve the optimal situation considered in the main part of this section, which is also the model studied in [10,11] via a stochastic master equation approach. The coupling parameter J is also assumed for simplicity to be equal for all TCQs and in particular J /2π = −400 MHz.…”

Section: Estimates Of Tcq Parametersmentioning

confidence: 99%

“…The added overhead of the required ancilla qubits is another deficiency of this paradigm. For this reason the quest for alternative ways of performing stabilizer measurements has become an active area of research [6][7][8][9][10][11][12][13][14][15].…”

Section: Introductionmentioning

confidence: 99%

“…Our approach begins with the scheme originally proposed in [9] and further analyzed in [10,11]. While this approach will work for any number of qubits, we focus on the useful case [16] of three qubits.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Three-qubit direct dispersive parity measurement with tunable coupling qubits

Ciani

DiVincenzo

2017

Phys. Rev. B

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We consider the direct three-qubit parity measurement scheme with two measurement resonators, using circuit quantum electrodynamics to analyze its functioning for several different types of superconducting qubits. We find that for the most common, transmon-like qubit, the presence of additional qubit-state-dependent coupling terms of the two resonators hinders the possibility of performing the direct parity measurement. We show how this problem can be solved by employing the tunable coupling qubit (TCQ) in a particular designed configuration. In this case, we effectively engineer the original model Hamiltonian by canceling the harmful terms. We further develop an analysis of the measurement in terms of information gains and provide some estimates of the typical parameters for optimal operation with TCQs.

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Section: B Parity Conditionmentioning

confidence: 49%

Section: Information Gain In Dispersive Parity Measurementmentioning

confidence: 99%

Section: Estimates Of Tcq Parametersmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Three-qubit direct dispersive parity measurement with tunable coupling qubits

Ciani

DiVincenzo

2017

Phys. Rev. B

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Machine learning for continuous quantum error correction on superconducting qubits

et al. 2022

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Continuous quantum error correction has been found to have certain advantages over discrete quantum error correction, such as a reduction in hardware resources and the elimination of error mechanisms introduced by having entangling gates and ancilla qubits. We propose a machine learning algorithm for continuous quantum error correction that is based on the use of a recurrent neural network to identity bit-flip errors from continuous noisy syndrome measurements. The algorithm is designed to operate on measurement signals deviating from the ideal behavior in which the mean value corresponds to a code syndrome value and the measurement has white noise. We analyze continuous measurements taken from a superconducting architecture using three transmon qubits to identify three significant practical examples of non-ideal behavior, namely auto-correlation at temporal short lags, transient syndrome dynamics after each bit-flip, and drift in the steady-state syndrome values over the course of many experiments. Based on these real-world imperfections, we generate synthetic measurement signals from which to train the recurrent neural network, and then test its proficiency when implementing active error correction, comparing this with a traditional double threshold scheme and a discrete Bayesian classifier. The results show that our machine learning protocol is able to outperform the double threshold protocol across all tests, achieving a final state fidelity comparable to the discrete Bayesian classifier.

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Breakdown signatures of the phenomenological Lindblad master equation in the strong optomechanical coupling regime

Betzholz¹,

Taketani²,

Torres³

2020

Quantum Sci. Technol.

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The Lindblad form of the master equation has proven to be one of the most convenient ways to describe the impact of an environment interacting with a quantum system of interest. For single systems the jump operators characterizing these interactions usually take simple forms with a clear interpretation. However, for coupled systems these operators take significantly different forms and the full dynamics cannot be described by jump operators acting on the individual subsystems only. In this work, we investigate the differences between a common phenomenological model for the master equation and the more rigorous dressed-state master equation for optomechanical systems. We provide an analytical method to obtain the absorption spectrum of the system for both models and show the breakdown of the phenomenological model in both the bad cavity and the ultra-strong coupling limit. We present a careful discussion of the indirect dephasing of the optical cavity in both models and its role in the differences of their predicted absorption spectra. Our work provides a simple experimental test to determine whether the simpler phenomenological model can be used to describe the system and is a step forward toward a better understanding of the role of the coupling between subsystems for open-quantum-system dynamics.

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Multi-qubit joint measurements in circuit QED: stochastic master equation analysis

Cited by 13 publications

References 35 publications

Three-qubit direct dispersive parity measurement with tunable coupling qubits

Three-qubit direct dispersive parity measurement with tunable coupling qubits

Machine learning for continuous quantum error correction on superconducting qubits

Breakdown signatures of the phenomenological Lindblad master equation in the strong optomechanical coupling regime

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