Shortcuts to Squeezed Thermal States

Abstract

Squeezed state in harmonic systems can be generated through a variety of techniques, including varying the oscillator frequency or using nonlinear two-photon Raman interaction. We focus on these two techniques to drive an initial thermal state into a final squeezed thermal state with controlled squeezing parameters – amplitude and phase – in arbitrary time. The protocols are designed through reverse engineering for both unitary and open dynamics. Control of the dissipation is achieved using stochastic processes, readily implementable via, e.g., continuous quantum measurements. Importantly, this allows controlling the state entropy and can be used for fast thermalization. The developed protocols are thus suited to generate squeezed thermal states at controlled temperature in arbitrary time.

Quantum optimal control in quantum technologies. Strategic report on current status, visions and goals for research in Europe

“…When further coupling the optomechanical system to a qubit, QOCT can exploit the non-linearity thereby introduced to prepare the mechanical oscillator in non-classical states [67]. In harmonic potentials, squeezed thermal states can be generated by a reverse engineering approach [203]. Time-dependent controls for spin squeezing in quantum metrology have been designed with reinforcement learning [547].…”

Time-dependent quantum harmonic oscillator: a continuous route from adiabatic to sudden changes

“…We expect our results to be useful in the construction of analytical expressions for the SP in HO's with arbitrary frequency modulations. Furthermore, the theoretical framework presented in this paper can be generalized to study the time evolution of any other initial state, including a thermal one, for instance, interesting in the realms of shortcuts to adiabaticity and quantum thermodynamics [51,53]. In such contexts, a clear understanding of the SPs in different basis and how they are related might be useful in the study of the third law of thermodynamics, quantum speed limits, or energetic cost of shortcuts.…”

“…In recent years, the TDHO has also received special attention in the contexts of shortcuts to adiabaticity and quantum thermodynamics. In the former, it is used in the determination of optimal nonadiabatic protocols that connect two equilibrium states with different frequencies, in such a way that the populations of the final and initial states are identical, a result that is obtained naturally through a perfectly adiabatic transformation [47][48][49][50][51]. In the latter, it can be considered as a working medium in a thermodynamical cycle [52,53], with the frequency changes being the quantum equivalent to the volumetric expansions and contractions of the medium.…”

Universal hybrid quantum computing in trapped ions

“…One-mode squeezing has been shown to enhance quantum metrology [21,23,46,47], the speed of entangling gates [48,49], and is an integral component of CVQC [2]. In trapped ions, squeezing of the motion can be generated through modulation of the trapping potential at twice the motional frequency [21,23], a diabatic change of the trapping frequency [21,50], a pair of laser beams with a difference frequency that is twice the motional frequency [28,51], or reservoir engineering [30]. Here, we present an alternative scheme, where each geometric phase gate interaction in Eq.…”