Cooper-pair current in the presence of flux noise

Abstract

We study the effect of flux noise on the Cooper pair current of a superconducting charge pump. We generalize the definition of the current in order to take into account the contribution induced by the environment. It turns out that this dissipative current vanishes for charge noise but it is finite in general for noise operators that do not commute with the charge operator. We discuss in a generic framework the effect of flux noise and present a way to engineer it by coupling the system to an additional external circuit. We calculate numerically the pumped charge through the device by solving the master equation for the reduced density matrix of the system and show how it depends on the coupling to the artificial environment.

Conservation law of operator current in open quantum systems

“…[5,6,[16][17][18][19] for recent theoretical progress in this field. Using a superadiabatic master equation based on a perturbative expansion, it has been shown for twolevel systems that the application of the secular approximation here results in nonconservation of the operator current [20]. The current was found to be conserved if the secular approximation was dropped.…”

Quantum effect of inductance on geometric Cooper-pair transport

“…12,25,32,33,[35][36][37]39 However, a model enabling one to use a non-negligible inductance for such transfer has not been studied previously. We write the geometric charge transferred by the mth adiabatic state in the usual manner: 12,15,25 …”

“…36,37 Both methods also have the potential for describing pumping when the driving is nonadiabatic, a regime recently studied experimentally. 38 Furthermore, a current induced directly by the environment has been shown to emerge for certain types of noise operators 39 leading to a development of a conservation law for all operator currents in open quantum systems. 40 To date, all considerations of the sluice have assumed an exact phase bias.…”

Environment-Governed Dynamics in Driven Quantum Systems

“…While this approach has successfully described a variety of quantum systems, it only offers a limited insight into the dynamics of decoherence. A promising line of work developed in the last decade exploits the possibility of coupling the system to an engineered reservoir [4][5][6][7][8][9][10][11][12].As new and more accurate ways are found of harnessing the dynamic evolution of quantum systems, it becomes increasingly important to understand how the interaction with the environment is affected by a time-dependent modulation of the system parameters. Indeed, the study of dissipation in driven quantum systems is a longestablished topic [13] that keeps finding new applications to quantum pumping [14][15][16], quantum computation [17,18], and possibly even biological systems [19,20].…”

“…While this approach has successfully described a variety of quantum systems, it only offers a limited insight into the dynamics of decoherence. A promising line of work developed in the last decade exploits the possibility of coupling the system to an engineered reservoir [4][5][6][7][8][9][10][11][12].…”