For quantum computers to become reality, not only do the qubits have to be carefully engineered to be well isolated during operation time, but this also puts great strain on the measurement setup. We have looked at the backaction from a single-electron transistor (SET), operated both in the normal and in the superconducting state, on a single Cooper-pair box qubit. We have also designed a new read-out setup for a flux qubit using a Cooper-pair transistor that would allow read-out at the flux degeneracy point. In the first case we calculate the mixing time and the influence on the qubit steady-state distribution. We find that the mixing time is larger than typical experimental measurement times, indicating the possibility of single shot read-out. For the steady-state distribution of the qubit, we calculate the Coulomb staircase, finding additional structure due to the noise in the SET. For the flux qubit we design a read-out scheme involving a quantum flip-flop process, where the measurement outcome results in the presence or absence of an incoherent tunneling process. We estimate read-out and mixing times and find that single shot read-out should be achievable.For quantum computers to become reality, not only do the qubits have to be carefully engineered to be well isolated during operation time, but this also puts great strain on the measurement setup. We have looked at the backaction from a single-electron transistor (SET), operated both in the normal and in the superconducting state, on a single Cooper-pair box qubit. We have also designed a new read-out setup for a flux qubit using a Cooper-pair transistor that would allow read-out at the flux degeneracy point. In the first case we calculate the mixing time and the influence on the qubit steady-state distribution. We find that the mixing time is larger than typical experimental measurement times, indicating the possibility of single shot read-out. For the steady-state distribution of the qubit, we calculate the Coulomb staircase, finding additional structure due to the noise in the SET. For the flux qubit we design a read-out scheme involving a quantum flip-flop process, where the measurement outcome results in the presence or absence of an incoherent tunneling process. We estimate read-out and mixing times and find that single shot read-out should be achievable.

Jan 1, 20040 citations

Fluxon readout for superconducting qubits

Kirill G. Fedorov, Anastasia V. Shcherbakova, Alexey Vladimirovich Ustinov

Bulletin of the American Physical SocietyMar 5, 20140 citations

Possible implementation of adiabatic quantum algorithm with superconducting flux qubits

M. Grajcar, A. Izmalkov, Evgeni V. Il’ichev

We show that an $LC$ parametric transducer can be effectively used to monitor an adiabatic evolution of the superconducting flux qubit. We propose a scheme to measure the qubit's state, which is a quantum nondemolition measurement. The scheme can be easily extended to a three-qubit system and allows the reading out of the qubits' states while the system remains in the ground state. An implementation of the adiabatic quantum algorithm MAXCUT for three superconducting flux qubits is discussed.We show that an $LC$ parametric transducer can be effectively used to monitor an adiabatic evolution of the superconducting flux qubit. We propose a scheme to measure the qubit's state, which is a quantum nondemolition measurement. The scheme can be easily extended to a three-qubit system and allows the reading out of the qubits' states while the system remains in the ground state. An implementation of the adiabatic quantum algorithm MAXCUT for three superconducting flux qubits is discussed.

arXiv:cond-mat/0407405Physical Review BApr 4, 200548 citations

Noise spectroscopy through dynamical decoupling with a superconducting flux qubit

Jonas Bylander, Simon Gustavsson, Fei Yan +7 more

arXiv:1101.4707Nature PhysicsMay 8, 2011866 citations

We show that an

LC

parametric transducer can be effectively used to monitor an adiabatic evolution of the superconducting flux qubit. We propose a scheme to measure the qubit's state, which is a quantum nondemolition measurement. The scheme can be easily extended to a three-qubit system and allows the reading out of the qubits' states while the system remains in the ground state. An implementation of the adiabatic quantum algorithm MAXCUT for three superconducting flux qubits is discussed.