Fast partial decoherence of a superconducting flux qubit in a spin bath

Jacek Dziarmaga

doi:10.1103/PhysRevB.71.054516

← Back to search

Fast partial decoherence of a superconducting flux qubit in a spin bath

Jacek Dziarmaga

DOI 10.1103/PhysRevB.71.054516 · Physical Review B

T1

Active bibliographic source — not scientific approval

Bibliographic access preserves source history; it does not approve extracted materials or validate reported claims. Review warnings on each occurrence separately.

Abstract

The superconducting flux qubit has two quantum states with opposite currents which generate different magnetic fields. Environment of nuclear spins can find out the magnetic field after a decoherence time τ0 inversely proportional to the magnetic field and the square root of the number of spins. When the Hamiltonian of the qubit drives fast coherent Rabi oscillations between the states with opposite current, then the magnetic field is flipped at a constant rate ω and the decoherence time τ=ωτ02 is much longer than τ0. However, on closer inspection decoherence actually takes place on two time scales. The long time τ is a time of full decoherence but a part of quantum coherence is lost already after the much shorter time π∕ω. This fast partial decoherence biases coherent flux oscillations towards the initial flux direction and it can affect performance of the superconducting devices as qubits.