Engineering Dissipative Channels for Realizing Schrödinger Cats in SQUIDs

Abstract

We show that by engineering the interaction with the environment, there exists a large class of systems that can evolve irreversibly to a cat state. To be precise, we show that it is possible to engineer an irreversible process so that the steady state is close to a pure Schrödinger's cat state by using double well systems and an environment comprising two-photon (or phonon) absorbers. We also show that it should be possible to prolong the lifetime of a Schrödinger's cat state exposed to the destructive effects of a conventional single-photon decohering environment. In addition to our general analysis, we present a concrete circuit realization of both system and environment that should be fabricatable with current technologies. Our protocol should make it easier to prepare and maintain Schrödinger cat states, which would be useful in applications of quantum metrology and information processing as well as being of interest to those probing the quantum to classical transition.

Hybrid Systems for the Generation of Nonclassical Mechanical States via Quadratic Interactions

“…In this work, we present hybrid setups that are able to achieve a two-phonon coherent coupling between a mechanical mode and a spin qubit, described as a two-level system (TLS). It is known for systems involving some kind of twoparticle interaction plus a nonlinearity [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36], that the mechanical system can evolve into motional cat states. Although these states are ultimately washed out by decoherence, our proposed setup features non-classical transient states, characterized by a negative Wigner function, during timescales that can extend up to seconds.…”

“…Transient non-classical states.-The high quality factors of state-of-the-art nanoresonators [65] allows for nonclassical states to develop and evolve in timescales of tenth of a second before every trace of coherence is washed out. We show this by plotting the evolution of the "cattiness" C = N (ρ)/N (ρ cat ), defined by dividing the integrated negative parts of the Wigner function of the state by that of a reference cat state [32], so that C > 0 only for nonclassical states and = 1 for cat states. The results shown in Fig.…”

Entanglement dynamics of quantum oscillators nonlinearly coupled to thermal environments

“…Systems with such symmetries are thus strong candidates for studying NLD in the quantum regime. Moreover, it was suggested that engineering of NLD might be feasible [29][30][31]. Exploiting the reduced disentanglement in systems with NLD is a promising path towards realizing entanglement based technologies.…”

“…Among these are carbon-based nanomechanical systems like graphene and carbon nanotubes [25,27,28]. Additionally, there have been reports of inducing nonlinear dissipation in optome- * Electronic address: andreas.isacsson@chalmers.se chanical systems [29,30], and suggestions for possible emergence of NLD in solid state quantum devices [31].…”

Deterministic amplification of Schrödinger cat states in circuit quantum electrodynamics

“…Sufficiently large SCSs for applications in quantum information ( 2 a » ) [18,19] and generalized Fock states [20] have recently been generated in microwave cavities with the assistance of superconducting qubits. Moreover, enhanced stabilization of SCSs in a cavity has recently been reported using a specially designed lossy environment [18,21], with the aim of producing robust quantum memory [22]. This loss engineering could also provide a complementary (continuous) method of SCS amplification in circuit QED.…”