Dynamical suppression of telegraph and1∕fnoise due to quantum bistable fluctuators

Abstract

We study dynamical decoupling of a qubit from non gaussian quantum noise due to discrete sources, as bistable fluctuators and 1/f noise. We obtain analytic and numerical results for generic operating point. For very large pulse frequency, where dynamic decoupling compensates decoherence, we found universal behavior. At intermediate frequencies noise can be compensated or enhanced, depending on the nature of the fluctuators and on the operating point. Our technique can be applied to a larger class of non-gaussian environments.

Hidden entanglement in the presence of random telegraph dephasing noise

“…In these systems entanglement revivals may also be induced by applying local pulses to the qubits [13,14,34].…”

Relaxation and decoherence in a resonantly driven qubit

“…Thus the relaxation and decoherence can not be suppressed simultaneously with a single resonant driving field. [42,43,44,45,46,47] Nevertheless, as will be demonstrated below, for a special class of initial states, a properly chosen resonant driving field could slow down the decoherence. [64] Since in general the population and coherence of a driven qubit decay with more than one rates, it is necessary to introduce multiple relaxation and decoherence times to describe the system's behavior properly.…”

“…[2,13,14,15,16] The environment-induced decoherence of superconducting qubits has been extensively studied both theoretically [15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33] and experimentally [2,8,13,21,25,34,35,36,37,38,39,40] in the absence of ac driving fields (free decay). Quite a few proposals, such as dynamical decoupling, [41,42,43,44,45,46,47,48] decoherence free subspaces, [49,50,51,52] spin echoes, [2,7,…”

Improving the Purity of One‐ and Two‐qubit Gates

“…One of the most prominent examples is the application of a sequence of π-pulses that flip the sign of the qubit-bath coupling operator resulting in a so-called dynamical decoupling (DD) of the qubit from the bath [17][18][19][20][21]23]. A drawback of this scheme is the fact that it eliminates only noise sources with a frequency below the repetition rate of the pulses.…”

“…The unavoidable coupling to external degrees of freedom and the thereby caused decoherence still presents a main obstacle for the realization of a quantum computer. Several proposals to overcome the ensuing decoherence have been put forward, such as the use of decoherence free subspaces [8][9][10][11][12], coherence-preserving qubits [13], quantum Zeno subspaces [14], optimized pulse sequences [15,16], dynamical decoupling [17][18][19][20][21], and coherent destruction of tunneling [22,23]. Theoretical studies of decoherence of two-level systems have been extended to gate operations in the presence of an environment in [24][25][26][27][28][29].…”