Emerging unitary evolutions in dissipatively coupled systems

Abstract

Having a broad range of methods available for implementing unitary operations is crucial for quantum information tasks. We study a dissipative process commonly used to describe dissipatively coupled systems and show that the process can lead to pure unitary dynamics on one part of a bipartite system, provided that the process is strong enough. If suitably engineered, the process allows to implement generic unitary operations. In fact, we show within the framework of quantum control theory that the dissipative process can turn the system of interest into a system capable of universal quantum information task. We characterize the time scales necessary to implement gates with high fidelity through the dissipative evolution. The considered dissipative evolution is of particular importance since it can be engineered in the laboratory in the realm of superconducting circuits. Based on a reservoir that is formed by a lossy microwave mode we present a detailed study of how our theoretical findings can be realized in an experimental setting.

Quantum nonreciprocal interactions via dissipative gauge symmetry

“…We stress that the mechanism of Eq. ( 3) is completely distinct from previous works exploring alternative dissipative approaches to quantum control [24][25][26][27][28][29][30][31].…”

“…( 16) has of course multiple steady states, something that is exploited by our protocol. Alternatively, other works utilize dynamics with steady-state degeneracy, and propose to use strong dissipation [25][26][27], measurements [28][29][30], or fast repetitive resets [31] to mimic Hamiltonian evolution of a target system. Unlike our work, there is no stabilization here: one needs to shut off the dynamics at a particular time in order to achieve a particular unitary (whereas we achieve the unitary in the long-time steady state).…”

Adiabatic elimination for ensembles of emitters in cavities with dissipative couplings

“…In particular, we highlight that those dissipative couplings can also lead to effective coherent Hamiltonian terms between A and the cavity. While the general effect of dissipatively engineered coherent interactions has been well studied for quantum information applications [20][21][22][23][24][25], we point out that it may also be important for cavitycoupled molecular systems. In this work we furthermore study the limitations of achievable effective parameters in the subsystem S consisting of A and the cavity, and we observe that the effective dynamics of S features collective decay processes.…”

Floquet theory for temporal correlations and spectra in time-periodic open quantum systems: Application to squeezed parametric oscillation beyond the rotating-wave approximation

“…Let us also remark that the operators in (36) are slowly-varying or rotating-picture operators, but we keep the same notation as before for simplicity, and because these are actually the operators that homodyne detection is sensitive to, so they are the ones we will use to compute the relevant spectral densities.…”

“…The use of modulations has been proposed, for instance, for generating two-mode entangled states in superconducting circuit resonators [1], quantum squeezing of the mirror motion [2][3][4][5] or of the radiation field in optomechanical [6][7][8] and superconducting-circuit cavities [7], for producing entanglement between a mechanical and an optical mode or between two radiation modes [5,9,10], for entangling the motional degrees of freedom of two tethered and optically-trapped microdisks inside a cavity [11], for cooling the ground state of a mechanical oscillator [12], for measuring the position of a mechanical oscillator in an optomechanical backaction-evading scheme [13,14], for enhancing nonlinear interactions in quantum optomechanics [15], or for synchronization or entrainment purposes [16][17][18][19][20][21][22][23][24][25] with its implications in the emergence of quantum correlations and entanglement [26,27]. Such periodic or multi-periodic drivings can also be used to engineer elusive dissipative models such as squeezed lasers [28], degenerate parametric oscillation [29,30], and non-reciprocal devices [31][32][33][34] with a range of applications [35][36][37]. Moreover, spontaneous periodic oscillations (also called limit cycles) can emerge in nonlinear syst...…”