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Simultaneously estimating multiple parameters at the ultimate limit is a central challenge in quantum metrology, often hindered by inherent incompatibilities in optimal estimation strategies. At its most extreme, this incompatibility…

We discuss the behavior of a two-level system coupled to a quantum dot contacted by superconducting source/drain electrodes, representing a simple model for the conformational degree of freedom of a molecular dot or a break junction. The…

Superconductivity · Physics 2009-11-13 A. Zazunov , A. Schulz , R. Egger

We report a superconducting artificial atom with an observed quantum coherence time of T2*=95us and energy relaxation time T1=70us. The system consists of a single Josephson junction transmon qubit embedded in an otherwise empty copper…

Precision measurements of frequency are critical to accurate timekeeping, and are fundamentally limited by quantum measurement uncertainties. While for time-independent quantum Hamiltonians, the uncertainty of any parameter scales at best…

Quantum Physics · Physics 2017-11-08 M. Naghiloo , A. N. Jordan , K. W. Murch

Proximity induced quantum coherence of electrons in multi-terminal voltage-driven hybrid normal-superconducting nanostructures may result in a non-trivial interplay between topology-dependent Josephson and Aharonov-Bohm effects. We…

Mesoscale and Nanoscale Physics · Physics 2020-05-05 Pavel E. Dolgirev , Mikhail S. Kalenkov , Andrei D. Zaikin

Quantum random number generators are a burgeoning technology used for a variety of applications, including modern security and encryption systems. Typical methods exploit an entropy source combined with an extraction or bit generation…

Since the first demonstration of coherent control of a quantum state of a superconducting charge qubit a variety of Josephson-junction-based qubits have been implemented with remarkable progress in coherence time and read-out schemes.…

Mesoscale and Nanoscale Physics · Physics 2009-11-10 T. Yamamoto , Yu. A. Pashkin , O. Astafiev , Y. Nakamura , J. S. Tsai

Nanotechnology has not only provided us the possibility of developing quantum machines but also noncanonical power sources able to drive them. Here we focus on studying the performance of quantum machines driven by arbitrary combinations of…

Mesoscale and Nanoscale Physics · Physics 2020-08-26 Sebastian E. Deghi , Raúl A. Bustos-Marún

We present a scheme for a self-testing quantum random number generator. Compared to the fully device-independent model, our scheme requires an extra natural assumption, namely that the mean energy per signal is bounded. The scheme is…

We develop a detailed theory describing a non-trivial interplay between non-equilibrium effects and long-range quantum coherence in superconducting hybrid nanostructures exposed to a temperature gradient. We establish a direct relation…

Superconductivity · Physics 2021-04-05 Mikhail S. Kalenkov , Andrei D. Zaikin

High-fidelity, efficient quantum nondemolition readout of quantum bits is integral to the goal of quantum computation. As superconducting circuits approach the requirements of scalable, universal fault tolerance, qubit readout must also…

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Strongly Correlated Electrons · Physics 2007-05-23 F. Siano R. Egger

Superconducting circuits incorporating Josephson tunnel junctions are widely used for fundamental research as well as for applications in fields such as quantum information and magnetometry. The quantum coherent nature of Josephson…

Mesoscale and Nanoscale Physics · Physics 2021-11-04 L. Peyruchat , J. Griesmar , J. -D. Pillet , Ç. Ö. Girit

Different nanofabricated superconducting circuits based on Josephson junctions have already achieved a degree of quantum coherence sufficient to demonstrate coherent superpositions of their quantum states. These circuits are considered for…

Superconductivity · Physics 2009-11-10 E. Collin , G. Ithier , A. Aassime , P. Joyez , D. Vion , D. Esteve

Although the emergence of a fully-functional quantum computer may still be far away from today, in the near future, it is possible to have medium-size, special-purpose, quantum devices that can perform computational tasks not efficiently…

Quantum Physics · Physics 2017-06-28 Man-Hong Yung , Xun Gao

Synchronization of Bloch oscillations in small Josephson junctions (JJs) under microwave radiation, which leads to current quantization, has been proposed as an effect that is dual to the appearance of Shapiro steps. This current…

We theoretically put forward the concept of a phase-controlled superconducting heat-flux quantum modulator. Its operation relies on phase-dependent heat current predicted to occur in temperature-biased Josephson tunnel junctions. The device…

Mesoscale and Nanoscale Physics · Physics 2012-10-02 F. Giazotto , M. J. Martinez-Perez

We have developed a set of seven observational equations that include all of the physics necessary to relate the most important of the fundamental constants to the definitions of the SI kilogram and ampere. We have used these to determine…

Atomic Physics · Physics 2015-05-13 Martin J. T. Milton , Jonathan M. Williams , Alistair B. Forbes

We perform switching current measurements of planar Josephson junctions (JJs) coupled by a common superconducting electrode, with independent control over the two superconducting phase differences. We observe an anomalous phase shift in the…

We present theoretical results for the equilibrium Josephson current through an Anderson dot tuned into the magnetic regime, using Hirsch-Fye Monte Carlo simulations covering the complete crossover from Kondo-dominated physics to $\pi$…

Strongly Correlated Electrons · Physics 2009-11-10 F. Siano , R. Egger