Researchers have developed a high-order nested-commutator compensation (HNCC) algorithm that significantly improves the precision of Hamiltonian simulations using product formulas. This method addresses the limitation of traditional product formulas, whose circuit size scales polynomially with inverse precision, by achieving polylogarithmic precision dependence in circuit size. The key innovation lies in HNCC's ability to maintain the advantages of product formulas, such as requiring no ancillary qubits, while drastically reducing computational requirements for high precision.
The HNCC algorithm employs a truncated Baker-Campbell-Hausdorff expansion to represent high-order Trotter errors as products of nested commutators. These errors are compensated at the superoperator level through randomly sampled Pauli-rotation channels, thus avoiding the need for Hadamard tests and ancillary qubits. For a K-th order product formula applied to a k-local Hamiltonian on N qubits with Γ Pauli terms and local interaction strength g₀, HNCC estimates the trace of Oe^(-i tH)ρe^(i tH) to an additive precision ε||O||. This is achieved using O(ε⁻²) repetitions and a maximum gate count per circuit of O(N^(2/(2K+1)) (k g₀ t log(1/ε))^(1+1/(2K+1)) k(Γ+log(1/ε))).
The resulting time dependence of the algorithm matches that of a product formula of order 2K+1. Finite-size resource estimates for the periodic Heisenberg chain indicate that HNCC achieves the lowest CNOT and T-gate counts per circuit among the product-formula-based methods considered. This advancement is crucial for the feasibility of complex quantum simulations, where error reduction and resource optimization are decisive factors in achieving quantum advantage.