Multi-mode architectures for noise-resilient superconducting qubits

Abstract

Great interest revolves around the development of new strategies to efficiently store and manipulate quantum information in a robust and decoherence-free fashion. Several proposals have been put forward to encode information into qubits that are simultaneously insensitive to relaxation and to dephasing processes. Among all, given their versatility and high-degree of control, superconducting qubits have been largely investigated in this direction. Here, we present a survey on the basic concepts and ideas behind the implementation of novel superconducting circuits with intrinsic protection against decoherence at a hardware level. In particular, the main focus is on multi-mode superconducting circuits, the paradigmatic example being the so-called $0-\pi$ circuit. We report on their working principle and possible physical implementations based on conventional Josephson elements, presenting recent experimental realizations, discussing both fabrication methods and characterizations.

Quantum information processing with superconducting circuits: a perspective

“…A recent comprehensive review by Calzona et al [199] describes and analyzes the basic concepts and ideas behind the implementation of novel superconducting circuits with intrinsic protection against decoherence at the hardware level. The review explains the basics and performance of state-of-the-art transmons and other single-mode superconducting quantum circuits, and goes on to describe multi-mode superconducting qubits, toward the realization of fully protected qubits engineered in systems with more than one degree of freedom and/or characterized by the presence of specific symmetries.…”

Lossy Micromaser Battery: Almost Pure States in the Jaynes–Cummings Regime

“…In this paper, we show first of all that the battery stability is obtained only in the case of coherent charging, while in the incoherent case slight deviations from the ideal, fine-tuned conditions, can effectively burn the battery. Moreover, the reported excellent properties, in the coherent case, of a micromaser as a quantum battery call for a deep analysis of its stability in the presence of decoherence mechanisms such as quantum noise [ 18 , 58 , 59 , 60 , 61 ]. Here, we consider the Jaynes–Cummings regime [ 62 ], where counter-rotating terms in the qubit-cavity collisions are neglected.…”

Hybrid quantum thermal machines with dynamical couplings

“…Basic questions like the same definitions of work and heat in small systems [11,12,16], where quantum mechanics inevitably comes into play, have to be reconsidered with care and are vital to properly characterize the working of nanoscale thermal machines. The minimum temperature achievable in a finite time in small system [17][18][19][20] is not only a fundamental question related to the third law of thermodynamics but also a practical question for cryogenic applications [10,13] and in the initialization of qubits in a quantum computer [21][22][23]. The development of protocols for heat flow control [13,24] is the key point to evacuate heat and cool hot spots in nanodevices.…”

“…On the other hand, driving the system and/or the system-bath couplings offers enhanced design flexibility, and the possibility to switch from some thermodynamic tasks to others simply by tuning the driving frequency. Here, we consider as a working medium (WM) the paradigmatic model of a quantum harmonic oscillator (QHO), which represents a basic building block in several quantum technology platforms [15,23,[41][42][43][44], coupled to three thermal reservoirs. We show that, by periodically modulating the couplings in a suitable way (see below for details and a physical illustration of our model), it is possible to efficiently run the thermal machine in a pure operation mode (engine, refrigerator, or heat pump), as well as in a hybrid mode, combining two of the above.…”