论文标题
无附件连续变量互换测试
Ancilla-free continuous-variable SWAP test
论文作者
论文摘要
我们提出了一项连续变量（CV）掉期测试，不需要Ancilla登记册，从而推广了无actilla的量换量子测试。在此无ANCILLA CV交换测试中，计算基础测量被光子数分解测量取代，我们计算了从检测器中有限的FOCK临界值获得的重叠估计误差的上限。例如，我们表明，可以使用低于Fock基础临界值$ O（e \lnε^{-1}）$的光子统计信息来获得对纯，中心的单模高斯能量$ e $的重叠的估计，并以相反的四倍挤压到相反的四倍。当状态迅速衰减的尾巴（例如连贯的状态）时，此截止量将大大减少为$ e + o（\ sqrt {e} \lnε^{ - 1}）$。我们展示了如何将无附提CV交换测试扩展到许多模式，并应用于CV设置中的量子算法，例如变异编译和纠缠光谱。对于后者，我们还提供了一种新的算法，该算法在量子系统中没有类似物。无需Ancilla CV交换测试是在Xanadu的8模式光子处理器上实施的，以估计两种模式挤压状态的真空概率。
We propose a continuous-variable (CV) SWAP test that requires no ancilla register, thereby generalizing the ancilla-free SWAP test for qubits. In this ancilla-free CV SWAP test, the computational basis measurement is replaced by photon number-resolving measurement, and we calculate an upper bound on the error of the overlap estimate obtained from a finite Fock cutoff in the detector. As an example, we show that estimation of the overlap of pure, centered, single-mode Gaussian states of energy $E$ and squeezed in opposite quadratures can be obtained to error $ε$ using photon statistics below a Fock basis cutoff $O(E\ln ε^{-1})$. This cutoff is greatly reduced to $E + O(\sqrt{E}\ln ε^{-1})$ when the states have rapidly decaying Fock tails, such as coherent states. We show how the ancilla-free CV SWAP test can be extended to many modes and applied to quantum algorithms such as variational compiling and entanglement spectroscopy in the CV setting. For the latter we also provide a new algorithm which does not have an analog in qubit systems. The ancilla-free CV SWAP test is implemented on Xanadu's 8-mode photonic processor in order to estimate the vacuum probability of a two-mode squeezed state.
