Robust Dynamical Decoupling for Quantum Computing and Quantum Memory

Abstract

Dynamical decoupling (DD) is a popular technique for protecting qubits from the environment. However, unless special care is taken, experimental errors in the control pulses used in this technique can destroy the quantum information instead of preserving it. Here, we investigate techniques for making DD sequences robust against different types of experimental errors while retaining good decoupling efficiency in a fluctuating environment. We present experimental data from solid-state nuclear spin qubits and introduce a new DD sequence that is suitable for quantum computing and quantum memory.

Robust dynamical decoupling

“…The shortest sequence that fulfils this condition is the XY-4 sequence [35,44]. An actual implementation must take into account, in addition to the earliermentioned issues, the effect of pulse imperfections [45,[54][55][56][57][58]. Fighting the effect of pulse errors was in fact the original motivation for the development of the XY-4 sequence [35].…”

“…Clearly, this procedure is limited by finite field strengths and associated pulse durations. Within these limitations, the goal remains to find those sequences that provide the best possible decoupling performance [45,54,55,67,[81][82][83][84]. Furthermore, the pulses do not only have finite lengths, they also do not implement perfect rotations.…”

“…The method is known as dynamical decoupling (DD). Since its initial introduction [44], a lot of effort has been invested to find sequences with improved error suppression [45][46][47][48][49][50][51][52][53][54]. The optimal design of DD sequences depends on the different sources of errors.…”

“…The DD technique is becoming an important tool for QIP [49,[54][55][56]59-67] as well as in spectroscopy [68][69][70][71] and imaging [72][73][74][75]. In most cases, the goal is to preserve a given input state, but it may also be combined with gate operations [76][77][78][79][80].…”

Storage of quantum coherences as phase-labelled local polarization in solid-state nuclear magnetic resonance

“…In all the samples mentioned already, the spin-spin decay time measured with a Hahn echo sequence (T HE 2 ) [34] was about an order of magnitude longer than the FID characteristic time (T * 2 ), evidencing the line inhomogeneity. Magnetization tails have been observed in 29 Si, C 60 and Y 2 O 3 [13,41,42], in adamantane under 1 H decoupling [57] and indirectly in 31 P in EPR experiments [20].…”