Dynamical decoupling of qubits in a spin bath under periodic quantum control
- Department of Physics, National Tsing Hua University, Hsinchu, Taiwan (China)
We investigate the feasibility for the preservation of coherence and entanglement of one- and two-spin qubits coupled to an interacting quantum spin-1/2 chain within the dynamical decoupling (DD) scheme. The performance is examined by counting the number of computing pulses that can be applied periodically with periods of T before qubits become decoherent, while an identical decoupling pulse sequence is applied within each cycle. By considering pulses with mixed directions and finite width controlled by magnetic fields, it is shown that pulse-width accumulation degrades the performance of sequences with larger numbers of pulses and that feasible magnetic fields in practice restrict consideration to sequences with few than 10 decoupling pulses within each cycle. Furthermore, within each cycle T, exact nontrivial pulse sequences are found to suppress the qubit-bath coupling to O(T{sup N+1}) progressively with the minimum number of pulses being 4, 7, and 12 for N=1,2,3. These sequences, when applied to all qubits, are shown to preserve both the entanglement and coherence. Based on time-dependent density matrix renormalization, our numerical results show that for modest magnetic fields (10-40 T) available in laboratories, the overall performance is optimized when the number of pulses in each cycle is 4 or 7 with pulse directions alternating between x and z. Our results provide useful guides for the preservation of coherence and entanglement of spin qubits in the solid state.
- OSTI ID:
- 21528828
- Journal Information:
- Physical Review. A, Vol. 82, Issue 6; Other Information: DOI: 10.1103/PhysRevA.82.062120; (c) 2010 American Institute of Physics; ISSN 1050-2947
- Country of Publication:
- United States
- Language:
- English
Similar Records
Universal dynamical decoupling: Two-qubit states and beyond
Optimal pulse spacing for dynamical decoupling in the presence of a purely dephasing spin bath