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Abstract
The Uhrig dynamical decoupling sequence achieves high-order decoupling of a single system qubit from its dephasing bath through the use of bang–bang Pauli pulses at appropriately timed intervals. High-order decoupling of single and multiple qubit systems from baths causing both dephasing and relaxation can also be achieved through the nested application of Uhrig sequences, again using single-qubit Pauli pulses. For the three-qubit decoherence free subsystem (DFS) and related subsystem encodings, Pauli pulses are not naturally available operations; instead, exchange interactions provide all required encoded operations. Here we demonstrate that exchange interactions alone can achieve high-order decoupling against general noise in the three-qubit DFS. We present decoupling sequences for a three-qubit DFS coupled to classical and quantum baths and evaluate the performance of the sequences through numerical simulations.
Highlights
Dynamical decoupling (DD) pulse sequences have had a long history beginning with the Hahn spin echo [1] and the Carr-Purcell-Meiboom-Gill sequences [2, 3] and continuing to the present
The Uhrig dynamical decoupling (UDD) sequence decouples a single qubit from a classical dephasing bath [4, 5]
We have shown that exchange pulses alone are sufficient to decouple the 3-qubit decoherence free subsystem (DFS) from classical and quantum baths
Summary
Dynamical decoupling (DD) pulse sequences have had a long history beginning with the Hahn spin echo [1] and the Carr-Purcell-Meiboom-Gill sequences [2, 3] and continuing to the present. The difference in requirements between single and two qubit gates has led to the development of encodings that use the exchange interaction alone [14, 15, 16]. The smallest such encoding is the 3-qubit decoherence free subsystem (DFS), for which explicit exchange gate sequences for encoded universal computation are given in [17, 18]. While encoded computation can be performed with exchange gates alone, the use of the DD pulse sequences described above would require single qubit Pauli operations. We assume “bang-bang” exchange pulses perform the decoupling, i.e., the pulses perform a perfect finite operation using infinite power in infinitesimal time
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