Perfect squeezing by damping modulation in circuit quantum electrodynamics

Abstract

Dissipation-driven quantum state engineering uses the environment to steer the state of quantum systems and preserve quantum coherence in the steady state. We show that modulating the damping rate of a microwave resonator generates a vacuum squeezed state of arbitrary squeezing strength, thereby constituting a mechanism allowing perfect squeezing. Given the recent experimental realizations in circuit QED of a microwave resonator with a tunable damping rate [Yin et al., Phys. Rev. Lett. 110, 107001 (2013)], superconducting circuits are an ideal playground to implement this technique. By dispersively coupling a qubit to the microwave resonator, it is possible to obtain qubit-state dependent squeezing.PACS numbers: 42.50. Dv, 03.65.Yz, 03.67.Lx. Introduction -The environment surrounding a quantum system induces decoherence and destroys quantum correlations. Quantum state engineering and manipulation is then limited by the coherence lifetime of the system. Surprisingly, if the coupling to the environment is controlled, it can be used as a resource to steer the system to a desired, fully coherent, quantum state. For example, it has been theoretically shown that this type of quantum bath engineering can be used for universal quantum computation [1,2] and to create robust quantum memories [3]. Possible realizations of quantum bath engineering have also been theoretically explored in the context of optical cavities [4,5], optomechanical systems [6], and circuit quantum electrodynamics (QED) [7,8]. Experimentally, dissipation-driven steady state entanglement has been obtained with atomic clouds [9], trapped ions [10], and superconducting circuits [11]. The preparation via damping of arbitrary superpositions in the state of a superconducting qubit has also been realized [12].Because of the improved measurement sensitivity that they provide, squeezed states are particularly interesting quantum states to stabilize [13]. In the optical domain, the standard approach to prepare such states is to pump a cavity containing a Kerr medium at twice the cavity frequency [14]. With this coherent approach, the variance of the intracavity squeezed quadrature is however at most reduced by a factor of 2. This is the well known 3 dB limit for squeezing [15]. Moreover the product of the variance of the two quadratures is larger than the Heisenberg limit; that is, the squeezing is not ideal.Motivated by a recent experiment in the field of circuit QED [16], we study the effect of periodically modulating the coupling between a microwave resonator and its environment, and we show that dissipation-driven squeezing can go beyond the limits encountered with the coherent generation of squeezed states. Indeed, we show that when the coupling strength of a microwave resonator to its environment is modulated at twice the resonator frequency ω r , the intra-resonator field can be ideally squeezed. The squeezed quadrature is arbitrarily reduced down to zero, beating the standard 3 dB limit and allowing perfect squeezing. The degree and axis of squeez...

Applications of the Fokker-Planck equation in circuit quantum electrodynamics

“…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].…”

Storage and on-demand release of microwaves using superconducting resonators with tunable coupling

“…This can be used for the fast initialization of a quantum bit 18 or for the creation of arbitrary strongly squeezed states of the field. 19 Our scheme uses a k=2 frequency-tunable resonator [8][9][10] intercalated between a k=4 fixed-frequency resonator and a transmission line (Fig. 1).…”

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

“…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.…”