Improved Bounded-Strength Decoupling Schemes for Local Hamiltonians
Adam D. Bookatz, Martin Roetteler, Pawel Wocjan · IEEE Transactions on Information Theory · 2016
We address the task of switching off the Hamiltonian of a system by removing all internal and system-environment couplings. We propose dynamical decoupling schemes that use only bounded-strength controls for quantum many-body systems with local system Hamiltonians and local environmental couplings. To do so, we introduce the combinatorial concept of balanced-cycle orthogonal arrays (BOAs) and show how to construct them from classical error-correcting codes. The derived decoupling schemes may be useful as a primitive for more complex schemes, e.g., for Hamiltonian simulation. For the case of n qubits and a two-local Hamiltonian, the length of the resulting decoupling scheme scales as O(n logn), improving over the previously best-known schemes that scaled quadratically with n. More generally, using BOAs constructed from families of Bose-Chaudhuri-Hocquenghem (BCH) codes, we show that bounded-strength decoupling for any ℓ-local Hamiltonian, where ℓ ≥ 2, can be achieved using decoupling schemes of length at most O(nℓ-1log n).