论文标题
动态，纠缠和马尔可夫噪声对少量数字量子模拟的保真度的影响
Impact of dynamics, entanglement, and Markovian noise on the fidelity of few-qubit digital quantum simulation
论文作者
论文摘要
已经提出了量子算法来加速在等离子体物理学中无处不在的混沌动力学系统的模拟。没有误差校正的量子计算机甚至可能利用噪声来利用其优势来计算Lyapunov指数，通过测量Loschmidt Echo Fidelity衰减率。在{IBM-Q}量子硬件平台上执行的量子锯齿图的数字汉密尔顿模拟首次表明，数字量子模拟的忠诚度衰减速率在从动态定位到地图中的混乱扩散的过渡期间增加。随着动力学从本地化到扩散，观察到的每个\ code {cnot}门的错误增加了$ 1.5 \ times $，而仅更改虚拟\ code {rz}门的阶段，并保持大门计数不变。一个基于门的lindblad噪声模型，该模型捕获了栅极操作期间放松和剥离错误的有效变化，从定性地解释了动态对忠诚度的影响，这是由于所创造的状态的定位和纠缠所致。具体而言，与随机相纠缠的高度离域状态显示出对脱落的敏感性，平均而言，对放松的敏感性与局部状态相似。相比之下，离域的未进入状态显示出对脱落的敏感性增加，但对放松的敏感性较低。通过估算\ code {cnot}门中的有效lindblad连贯时间，并找到一致的$ 2 \ text { - } 3 \ times $ shortter $ t_2 $，该$ t_2 $ shortter $ t_2 $，通过估计有效的lindblad连贯时间，这是一个有用的基准测试工具。因此，模拟的动力学与活动噪声过程的动力学相互作用会强烈影响总体保真度衰减率。
Quantum algorithms have been proposed to accelerate the simulation of the chaotic dynamical systems that are ubiquitous in the physics of plasmas. Quantum computers without error correction might even use noise to their advantage to calculate the Lyapunov exponent by measuring the Loschmidt echo fidelity decay rate. For the first time, digital Hamiltonian simulations of the quantum sawtooth map, performed on the {IBM-Q} quantum hardware platform, show that the fidelity decay rate of a digital quantum simulation increases during the transition from dynamical localization to chaotic diffusion in the map. The observed error per \code{CNOT} gate increases by $1.5\times$ as the dynamics varies from localized to diffusive, while only changing the phases of virtual \code{RZ} gates and keeping the over-all gate count constant. A gate-based Lindblad noise model that captures the effective change in relaxation and dephasing errors during gate operation qualitatively explains the effect of dynamics on fidelity as being due to the localization and entanglement of the states created. Specifically, highly delocalized states that are entangled with random phases show an increased sensitivity to dephasing and, on average, a similar sensitivity to relaxation as localized states. In contrast, delocalized unentangled states show an increased sensitivity to dephasing but a lower sensitivity to relaxation. This gate-based Lindblad model is shown to be a useful benchmarking tool by estimating the effective Lindblad coherence times during \code{CNOT} gates and finding a consistent $2\text{--}3\times$ shorter $T_2$ time than reported for idle qubits. Thus, the interplay of the dynamics of a simulation with the noise processes that are active can strongly influence the overall fidelity decay rate.
