Methodology for replacing indirect measurements with direct measurements
Methodology for replacing indirect measurements with direct measurements
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DOI：
10.1103/physrevresearch.1.013006
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发表时间：
2019-08-09
影响因子：
4.2
通讯作者：
Fujii, Keisuke
中科院分区：
文献类型：
--
作者：
Mitarai, Kosuke;Fujii, Keisuke
在量子计算中，幺正算符的间接测量（如阿达玛检验）在许多算法中起着重要作用。然而，在某些情况下，间接测量可以简化为直接测量，其中量子态被破坏性地测量。在这里，我们调查在什么条件下，这样的替代是可能的，并制定了一个一般的方法来交易的间接测量与连续的直接测量。这些结果可以用来构造量子电路，计算参数化量子态的解析梯度、度规张量、海森函数，甚至高阶导数。此外，我们提出了一种方法来衡量的时间顺序相关器的基础上提出的协议。我们的协议可以显着减少量子电路的深度，使控制操作不必要的，因此适合于量子经典混合算法在近期量子计算机。
In quantum computing, the indirect measurement of unitary operators such as the Hadamard test plays a significant role in many algorithms. However, in certain cases, the indirect measurement can be reduced to the direct measurement, where a quantum state is destructively measured. Here, we investigate under what conditions such a replacement is possible and develop a general methodology for trading an indirect measurement with sequential direct measurements. The results can be applied to construct quantum circuits to evaluate the analytical gradient, metric tensor, Hessian, and even higher order derivatives of a parametrized quantum state. Also, we propose a method to measure the out-of-time-order correlator based on the presented protocol. Our protocols can significantly reduce the depth of a quantum circuit by making the controlled operation unnecessary, and thus are suitable for quantum-classical hybrid algorithms on near-term quantum computers.