5 research outputs found
Quantum logic gates for coupled superconducting phase qubits
Based on a quantum analysis of two capacitively coupled current-biased
Josephson junctions, we propose two fundamental two-qubit quantum logic gates.
Each of these gates, when supplemented by single-qubit operations, is
sufficient for universal quantum computation. Numerical solutions of the
time-dependent Schroedinger equation demonstrate that these operations can be
performed with good fidelity.Comment: 4 pages, 5 figures, revised for publicatio
Spectroscopy of Three-Particle Entanglement in a Macroscopic Superconducting Circuit
We study the quantum mechanical behavior of a macroscopic, three-body,
superconducting circuit. Microwave spectroscopy on our system, a resonator
coupling two large Josephson junctions, produced complex energy spectra well
explained by quantum theory over a large frequency range. By tuning each
junction separately into resonance with the resonator, we first observe strong
coupling between each junction and the resonator. Bringing both junctions
together into resonance with the resonator, we find spectroscopic evidence for
entanglement between all three degrees of freedom and suggest a new method for
controllable coupling of distant qubits, a key step toward quantum computation.Comment: 4 pages, 3 figure
Geometric Quantum Computation on Solid-State Qubits
An adiabatic cyclic evolution of control parameters of a quantum system ends
up with a holonomic operation on the system, determined entirely by the
geometry in the parameter space. The operation is given either by a simple
phase factor (a Berry phase) or a non-Abelian unitary operator depending on the
degeneracy of the eigenspace of the Hamiltonian. Geometric quantum computation
is a scheme to use such holonomic operations rather than the conventional
dynamic operations to manipulate quantum states for quantum information
processing. Here we propose a geometric quantum computation scheme which can be
realized with current technology on nanoscale Josephson-junction networks,
known as a promising candidate for solid-state quantum computer.Comment: 6 figures; to appear in J. Phys.: Condens. Mat