Córcoles A D, Takita Maika, Inoue Ken, Lekuch Scott, Minev Zlatko K, Chow Jerry M, Gambetta Jay M
IBM Quantum, IBM T. J. Watson Research Center, Yorktown Heights, New York 10598, USA.
Phys Rev Lett. 2021 Sep 3;127(10):100501. doi: 10.1103/PhysRevLett.127.100501.
To date, quantum computation on real, physical devices has largely been limited to simple, time-ordered sequences of unitary operations followed by a final projective measurement. As hardware platforms for quantum computing continue to mature in size and capability, it is imperative to enable quantum circuits beyond their conventional construction. Here we break into the realm of dynamic quantum circuits on a superconducting-based quantum system. Dynamic quantum circuits not only involve the evolution of the quantum state throughout the computation but also periodic measurements of qubits midcircuit and concurrent processing of the resulting classical information on timescales shorter than the execution times of the circuits. Using noisy quantum hardware, we explore one of the most fundamental quantum algorithms, quantum phase estimation, in its adaptive version, which exploits dynamic circuits, and compare the results to a nonadaptive implementation of the same algorithm. We demonstrate that the version of real-time quantum computing with dynamic circuits can yield results comparable to an approach involving classical asynchronous postprocessing, thus opening the door to a new realm of available algorithms on real quantum systems.
迄今为止，在真实物理设备上进行的量子计算在很大程度上仅限于简单的、按时间顺序排列的酉操作序列，随后进行最终的投影测量。随着量子计算硬件平台在规模和能力上不断成熟，突破其传统结构来实现量子电路变得势在必行。在此，我们进入了基于超导量子系统的动态量子电路领域。动态量子电路不仅涉及量子态在整个计算过程中的演化，还包括在电路中间对量子比特进行周期性测量，以及在比电路执行时间更短的时间尺度上对所得经典信息进行并发处理。利用有噪声的量子硬件，我们探索了最基本的量子算法之一——量子相位估计的自适应版本，该版本利用了动态电路，并将结果与同一算法的非自适应实现进行比较。我们证明，具有动态电路的实时量子计算版本能够产生与涉及经典异步后处理的方法相当的结果，从而为真实量子系统上的可用算法开辟了一个新领域。
