2026/08/06 by Boyang Chen, Minbo Gao, Xinzhao Wang +1
Physics and Astronomy · Computer Science · #quant-ph #cs.DS
35 pages, 1 figure, 1 table
arxiv created 2026/08/06 · arxiv updated 2026/08/07
We give a query-optimal algorithm for simulating a general n-qubit time-dependent Hamiltonian H(t) on [0,T], assuming that H is Lipschitz continuous and ‖H(t)‖≤α. In the standard HAM-T access model, the algorithm approximates the time-ordered propagator UH(T) to error ε using O( αT+\fraclog(1/ε) log(e+log(1/ε)/(αT)) ) HAM-T queries. This matches the known query lower bound for time-independent Hamiltonians, showing that time dependence incurs no asymptotic query overhead. Our method first constructs a one-query transducer that, given an auxiliary state, implements an approximation to UH(T) and returns the state unchanged. A weighted combination of circuits that apply the transducer different numbers of times makes the error caused by omitting this state decay factorially, yielding the stated optimal precision dependence. For time-independent Hamiltonians, the same method also gives a query-optimal alternative to qubitization.