Optimized dynamical decoupling in a model quantum memory

Abstract

Any quantum system, such as those used in quantum information or magnetic resonance, is subject to random phase errors that can dramatically affect the fidelity of a desired quantum operation or measurement. In the context of quantum information, quantum error correction techniques have been developed to correct these errors, but resource requirements are extraordinary. The realization of a physically tractable quantum information system will therefore be facilitated if qubit (quantum bit) error rates are far below the so-called fault-tolerance error threshold, predicted to be of the order of 10(-3)-10(-6). The need to realize such low error rates motivates a search for alternative strategies to suppress dephasing in quantum systems. Here we experimentally demonstrate massive suppression of qubit error rates by the application of optimized dynamical decoupling pulse sequences, using a model quantum system capable of simulating a variety of qubit technologies. We demonstrate an analytically derived pulse sequence, UDD, and find novel sequences through active, real-time experimental feedback. The latter sequences are tailored to maximize error suppression without the need for a priori knowledge of the ambient noise environment, and are capable of suppressing errors by orders of magnitude compared to other existing sequences (including the benchmark multi-pulse spin echo). Our work includes the extension of a treatment to predict qubit decoherence under realistic conditions, yielding strong agreement between experimental data and theory for arbitrary pulse sequences incorporating nonidealized control pulses. These results demonstrate the robustness of qubit memory error suppression through dynamical decoupling techniques across a variety of qubit technologies.

Robust dynamical decoupling

“…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].…”

Finite-temperature decoherence of spin states in a {Cu3} single molecular magnet

“…Quantum decoherence is manifested when single molecular magnets are coupled to a spin bath [18][19][20][21]. The dissipation and decoherence always depend on the properties of the environment which can be described by a certain spectral density function [22][23][24][25].…”

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

“…Some of the strategies implemented with NMR and electron paramagnetic resonance (EPR), such as decoupling techniques [24][25][26][27][28], have a wide interest, as they can be adapted to many other two-level systems such as trapped ions, quantum dots [29] or Josephson junctions [30][31][32][33]. The renovated interest in pulse sequences that help to fight decoherence has revived the old sequences such as the Hahn echo [34], the Carr-Purcell (CP) [35] and the Carr-Purcell-Meiboom-Gill (CPMG) [36], and it has stimulated the development of new ones [37,38].…”