Nearly optimal time-independent reversal of a spin chain
Nearly optimal time-independent reversal of a spin chain
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自旋链的近乎最优的与时间无关的反转
DOI：
10.1103/physrevresearch.4.l012023
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发表时间：
2020
影响因子：
4.2
通讯作者：
Andrew M. Childs
中科院分区：
文献类型：
--
作者：
A. Bapat;E. Schoute;A. Gorshkov;Andrew M. Childs
我们提出了一个时间无关的哈密顿协议，用于反转量子比特在$N$自旋链中的顺序。我们的协议具有易于实现的具有时间无关的非均匀耦合的最近邻横场Ising模型哈密顿量。在适当的规范化下，我们实现这种状态反转的速度比使用SWAP门的朴素方法快三倍，与Raussendorf[物理学家]的协议相当。[j] .机械工程学报，2014,(1):1 - 2。我们还利用哈密顿子纠缠能力的结果证明了状态反转的下界，并表明我们在可能的最短时间的因子$1.502(1+1/N)$范围内。我们的下界适用于所有具有任意有限辅助空间、局部操作和经典通信的最近邻量子比特协议。最后，我们将我们的协议扩展到一个无限的最近邻，时间无关的状态反转哈密顿协议族。这包括具有几乎均匀耦合的链，这种链可能特别适用于实验实现。
We propose a time-independent Hamiltonian protocol for the reversal of qubit ordering in a chain of $N$ spins. Our protocol has an easily implementable nearest-neighbor, transverse-field Ising model Hamiltonian with time-independent, non-uniform couplings. Under appropriate normalization, we implement this state reversal three times faster than a naive approach using SWAP gates, in time comparable to a protocol of Raussendorf [Phys. Rev. A 72, 052301 (2005)] that requires dynamical control. We also prove lower bounds on state reversal by using results on the entanglement capacity of Hamiltonians and show that we are within a factor $1.502(1+1/N)$ of the shortest time possible. Our lower bound holds for all nearest-neighbor qubit protocols with arbitrary finite ancilla spaces and local operations and classical communication. Finally, we extend our protocol to an infinite family of nearest-neighbor, time-independent Hamiltonian protocols for state reversal. This includes chains with nearly uniform coupling that may be especially feasible for experimental implementation.