Cotunneling in pairs of coupled flux qubits

  title={Cotunneling in pairs of coupled flux qubits},
  author={Trevor Lanting and R. Harris and J. Johansson and Mohammad H. S. Amin and Andrew J. Berkley and S. Gildert and M. William Johnson and Paul I. Bunyk and Elena Tolkacheva and Eric Ladizinsky and Nicolas Ladizinsky and Travis Oh and I. G. Perminov and E. M. Chapple and C. Enderud and Chris Rich and Brendan J Wilson and Murray C. Thom and Sergey Uchaikin and Geordie Rose},
  journal={Physical Review B},
Superconducting circuits have played an essential role in realizing quantum mechanical phenomena in macroscopic systems. One such example is the observation of macroscopic resonant tunneling (MRT) of magnetic flux between the lowest energy states of single rf-SQUID flux qubits, as demonstrated by several groups [1–4]. These measurements provide both a clear signature of quantum mechanics in a macroscopic circuit at a finite temperature and in the presence of noise and a direct means of… 

Figures from this paper

1 / f noise: Implications for solid-state quantum information
The efficiency of the future devices for quantum information processing will be limited mostly by the finite decoherence rates of the individual qubits and quantum gates. Recently, substantial
Thermally assisted quantum annealing of a 16-qubit problem.
It is experimentally demonstrated that, even with annealing times eight orders of magnitude longer than the predicted single-qubit decoherence time, the probabilities of performing a successful computation are similar to those expected for a fully coherent system.
Locally suppressed transverse-field protocol for diabatic quantum annealing
Diabatic quantum annealing (DQA) is an alternative algorithm to adiabatic quantum annealing that can be used to circumvent the exponential slowdown caused by small minima in the annealing energy
Computational multiqubit tunnelling in programmable quantum annealers
It is shown that 8-qubit tunnelling plays a computational role in a currently available programmable quantum annealer, and a nonperturbative theory of open quantum dynamics under realistic noise characteristics is developed that accurately predicts the rate of many-body dissipative quantum Tunnelling subject to the polaron effect.
Theory of open quantum dynamics with hybrid noise
We develop a theory to describe dynamics of a nonstationary open quantum system interacting with a hybrid environment, which includes high-frequency and low-frequency noise components. One part of
At the intersection of quantum computing and quantum chemistry
Quantum chemistry is concerned with solving the Schrodinger equation for chemically relevant systems. This is typically done by making useful and systematic approximations which form the basis for
Finite temperature quantum annealing solving exponentially small gap problem with non-monotonic success probability
The authors show a nonmonotonic behavior of a quantum annealing processor, explaining it in terms of thermally accessible states, consistent with a quantum open-system description that is unrelated to thermal relaxation, and is instead dominated by the system's properties at the critical point.
Simulating chemistry using quantum computers.
This review discusses to what extent the ideas in quantum computation, now a well-established field, have been applied to chemical problems and describes algorithms that achieve significant advantages for the electronic-structure problem, the simulation of chemical dynamics, protein folding, and other tasks.
Finding low-energy conformations of lattice protein models by quantum annealing
This report presents a benchmark implementation of quantum annealing for lattice protein folding problems (six different experiments up to 81 superconducting quantum bits) and paves the way towards studying optimization problems in biophysics and statistical mechanics using quantum devices.


Macroscopic quantum tunnelling of magnetization in a single crystal of nanomagnets
THE precise manner in which quantum-mechanical behaviour at the microscopic level underlies classical behaviour at the macroscopic level remains unclear, despite seventy years of theoretical
Experimental demonstration of a robust and scalable flux qubit
Received 23 September 2009; revised manuscript received 11 February 2010; published 7 April 2010 A rf–superconducting quantum interference device SQUID flux qubit that is robust against fabrication
Probing noise in flux qubits via macroscopic resonant tunneling.
Macroscopic resonant tunneling between the two lowest lying states of a bistable rf SQUID is used to characterize noise in a flux qubit and indicates that the dominant source of low energy flux noise is a quantum mechanical environment in thermal equilibrium.
dc measurements of macroscopic quantum levels in a superconducting qubit structure with a time-ordered meter
dc measurements are made in a superconducting, persistent current qubit structure with a time-ordered meter. The persistent-current qubit has a double-well potential, with the two minima
Landau-Zener transitions in a superconducting flux qubit
We report an experimental measurement of Landau-Zener transitions on an individual flux qubit within a multi-qubit superconducting chip designed for adiabatic quantum computation. The method used
Correlated flux noise and decoherence in two inductively coupled flux qubits
We have studied decoherence in a system where two Josephson-junction flux qubits share a part of their superconducting loops and are inductively coupled. By tuning the flux bias condition, we control
Localization of metal-induced gap states at the metal-insulator interface: origin of flux noise in SQUIDs and superconducting qubits.
It is shown that, in the presence of potential disorder at the metal-insulator interface, some of theMetal-induced gap states become localized and produce local moments and a modest level of disorder yields the observed areal density.
Macroscopic resonant tunneling of magnetic flux
We have developed a quantitative theory of resonant tunneling of magnetic flux between discrete macroscopically distinct quantum states in superconducting quantum interference device systems. The
Observation of Resonant Tunneling between Macroscopically Distinct Quantum Levels.
We report the first observation of resonant tunneling of a system between two macroscopically distinct states: energy levels in different fluxoid wells of a weakly damped superconducting quantum
We report experimental evidence of macroscopic quantum tunneling in antiferromagnetic particles. The zero-field maximum in the dependence of the magnetic relaxation rate on the magnetic field in