Toward a superconducting quantum computer Harnessing macroscopic quantum coherence:Harnessing macroscopic quantum coherence

Intensive research on the construction of superconducting quantum computers has produced numerous important achievements. The quantum bit (qubit), based on the Josephson junction, is at the heart of this research. This macroscopic system has the ability to control quantum coherence. This article reviews the current state of quantum computing as well as its history, and discusses its future. Although progress has been rapid, the field remains beset with unsolved issues, and there are still many new research opportunities open to physicists and engineers.Intensive research on the construction of superconducting quantum computers has produced numerous important achievements. The quantum bit (qubit), based on the Josephson junction, is at the heart of this research. This macroscopic system has the ability to control quantum coherence. This article reviews the current state of quantum computing as well as its history, and discusses its future. Although progress has been rapid, the field remains beset with unsolved issues, and there are still many new research opportunities open to physicists and engineers.

Proceedings of the Japan Academy Series BJan 1, 201011 citations

An Experiment to observe Macroscopic Quantum Coherence in an rf-SQUID

Xingxiang Zhou, Jonathan L. Habif, Pavel Rott +2 more

We present the design of an on-chip time domain experiment to demonstrate macroscopic quantum coherence in an rf-SQUID, a superconducting loop interrupted by a Josephson junction. If suc- cessful the SQUID will serve as a for a superconducting quantum computer. The chip is currently in fabrication. odinger' s parable, a clear demonstration of rf-SQUID MQC would dramatically challenge our concepts of the quantum / classical boundary. The rf-SQUID MQC state was proposed as a candidate to serve as the for a possible superconducting quantum computer (2). Very recently, spectroscopic experiments showed the energy level structure expected for MQC phenomena in an rf-SQUID (3) and in the very similar persistent current qubit (4). It is our intention to conduct a time domain experiment in which the macroscopic quantum coherent oscillations will be observed directly as they evolve. The Hamiltonian of the rf-SQUID system, under the assumption of no dissipation, isWe present the design of an on-chip time domain experiment to demonstrate macroscopic quantum coherence in an rf-SQUID, a superconducting loop interrupted by a Josephson junction. If suc- cessful the SQUID will serve as a for a superconducting quantum computer. The chip is currently in fabrication. odinger' s parable, a clear demonstration of rf-SQUID MQC would dramatically challenge our concepts of the quantum / classical boundary. The rf-SQUID MQC state was proposed as a candidate to serve as the for a possible superconducting quantum computer (2). Very recently, spectroscopic experiments showed the energy level structure expected for MQC phenomena in an rf-SQUID (3) and in the very similar persistent current qubit (4). It is our intention to conduct a time domain experiment in which the macroscopic quantum coherent oscillations will be observed directly as they evolve. The Hamiltonian of the rf-SQUID system, under the assumption of no dissipation, is

Optical Fiber Communication ConferenceJun 13, 20010 citations

Macroscopic Quantum Resonance of Coupled Flux Qubits; A Quantum Computation Scheme

Hide Akisato

We show that a superconducting circuit containing two loops, when treated with Macroscopic Quantum Coherence (MQC) theory, constitutes a complete two-bit quantum computer. The manipulation of the system is easily implemented with alternating magnetic fields. A \textit{universal} set of quantum gates is deemed available by means of all unitary single bit operations and a controlled-not (\textsc{cnot}) sequence. We use multi-dimensional MQC theory and time-dependent first order perturbation theory to analyze the model. Our calculations show that a two qubit arrangement, each having a diameter of 200nm, operating in the flux regime can be operated with a static magnetic field of $\sim 0.1$ T, and an alternating dynamic magnetic field of amplitude $\sim 1$ Gauss and frequency $\sim 10$ Hz. The operational time $τ_{op}$ is estimated to be $\sim 10$ ns.We show that a superconducting circuit containing two loops, when treated with Macroscopic Quantum Coherence (MQC) theory, constitutes a complete two-bit quantum computer. The manipulation of the system is easily implemented with alternating magnetic fields. A \textit{universal} set of quantum gates is deemed available by means of all unitary single bit operations and a controlled-not (\textsc{cnot}) sequence. We use multi-dimensional MQC theory and time-dependent first order perturbation theory to analyze the model. Our calculations show that a two qubit arrangement, each having a diameter of 200nm, operating in the flux regime can be operated with a static magnetic field of $\sim 0.1$T, and an alternating dynamic magnetic field of amplitude $\sim 1$ Gauss and frequency $\sim 10$Hz. The operational time $τ_{op}$ is estimated to be $\sim 10$ns.

arXiv:quant-ph/0303128Mar 20, 20030 citations

\sim 0.1

T, and an alternating dynamic magnetic field of amplitude

\sim 1

Gauss and frequency

\sim 10

Hz. The operational time

τ_{op}

is estimated to be

\sim 10

ns.