Enhancement and state tomography of a squeezed vacuum with circuit quantum electrodynamics

Elliott, Matthew; Ginossar, Eran

doi:10.1103/physreva.92.013826

Cited by 11 publications

(9 citation statements)

References 46 publications

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“…Therefore, we can conclude that the majority of error in the full state is due to the qubit-state error, and as such the cavity state is not appreciably affected by the higher-order nonlinearities in the Jaynes-Cummings interaction. Finally, we note that the effect of these higherorder terms has previously been investigated for injected squeezing [45].…”

Section: Signal-to-noise Ratiomentioning

confidence: 87%

Enhanced qubit readout using locally generated squeezing and inbuilt Purcell-decay suppression

Govia

Clerk

2017

New J. Phys.

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We introduce and analyze a dispersive qubit readout scheme where two-mode squeezing is generated directly in the measurement cavities. The resulting suppression of noise enables fast, high-fidelity readout of naturally weakly coupled qubits, and the possibility to protect strongly coupled qubits from decoherence by weakening their coupling. Unlike other approaches exploiting squeezing, our setup avoids the difficult task of transporting and injecting with high fidelity an externally generated squeezed state. Our setup is also surprisingly robust against unwanted non-QND backaction effects, as interference naturally suppresses Purcell decay: the system acts as its own Purcell filter. Our setup is compatible with the experimental state-of-the-art in circuit QED systems, but the basic idea could also be realized in other systems.

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Section: Signal-to-noise Ratiomentioning

confidence: 87%

Enhanced qubit readout using locally generated squeezing and inbuilt Purcell-decay suppression

Govia

Clerk

2017

New J. Phys.

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“…Generation and measurement of squeezing has been the subject of much recent research in the field of circuit QED [59][60][61][62]. When U = 0, it is known that the maximum squeezing the can be achieved is a factor of 2, reducing the fluctuations in one field quadrature to 50% of those of the vacuum state [1].…”

Section: Generation Of Squeezingmentioning

confidence: 99%

Applications of the Fokker-Planck equation in circuit quantum electrodynamics

Elliott

Ginossar

2016

Phys. Rev. A

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We study exact solutions of the steady state behaviour of several non-linear open quantum systems which can be applied to the field of circuit quantum electrodynamics. Using Fokker-Planck equations in the generalised P -representation we investigate the analytical solutions of two fundamental models. First, we solve for the steady-state response of a linear cavity that is coupled to an approximate transmon qubit and use this solution to study both the weak and strong driving regimes, using analytical expressions for the moments of both cavity and transmon fields, along with the Husimi Q-function for the transmon. Second, we revisit exact solutions of quantum Duffing oscillator which is driven both coherently and parametrically while also experiencing decoherence by the loss of single and pairs of photons. We use this solution to discuss both stabilisation of Schrödinger cat states and the generation of squeezed states in parametric amplifiers, in addition to studying the Q-functions of the different phases of the quantum system. The field of superconducting circuits, with its strong nonlinearities and couplings, has provided access to new parameter regimes in which returning to these exact quantum optics methods can provide valuable insights.

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“…As the qubit and cavity are far from resonance, we do not invoke the RWA to simplify the light-matter interaction; this also allows us to work with values of g/ω ranging up to ≈0.1. Although the theory presented here may describe many different types of experimental systems, the dispersive limit is particularly applicable to experiments in circuit QED1930316465 and qubit-coupled nanomechanics29, which we touch on near the end of the paper.…”

Section: Resultsmentioning

confidence: 99%

Qubit-flip-induced cavity mode squeezing in the strong dispersive regime of the quantum Rabi model

Joshi

Irish

Spiller

2017

Sci Rep

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Squeezed states of light are a set of nonclassical states in which the quantum fluctuations of one quadrature component are reduced below the standard quantum limit. With less noise than the best stabilised laser sources, squeezed light is a key resource in the field of quantum technologies and has already improved sensing capabilities in areas ranging from gravitational wave detection to biomedical applications. In this work we propose a novel technique for generating squeezed states of a confined light field strongly coupled to a two-level system, or qubit, in the dispersive regime. Utilising the dispersive energy shift caused by the interaction, control of the qubit state produces a time-dependent change in the frequency of the light field. An appropriately timed sequence of sudden frequency changes reduces the quantum noise fluctuations in one quadrature of the field well below the standard quantum limit. The degree of squeezing and the time of generation are directly controlled by the number of frequency shifts applied. Even in the presence of realistic noise and imperfections, our protocol promises to be capable of generating a useful degree of squeezing with present experimental capabilities.

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Enhancement and state tomography of a squeezed vacuum with circuit quantum electrodynamics

Cited by 11 publications

References 46 publications

Enhanced qubit readout using locally generated squeezing and inbuilt Purcell-decay suppression

Enhanced qubit readout using locally generated squeezing and inbuilt Purcell-decay suppression

Applications of the Fokker-Planck equation in circuit quantum electrodynamics

Qubit-flip-induced cavity mode squeezing in the strong dispersive regime of the quantum Rabi model

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