论文标题
自旋链的几乎最佳时间无关的逆转
Nearly optimal time-independent reversal of a spin chain
论文作者
论文摘要
我们建议在$ n $ spins的链条中逆转量子订购的时间无关的汉密尔顿协议。我们的协议具有易于实现的最近的邻居，横向场模型的哈密顿量，并具有时间独立，不均匀的耦合。在适当的归一化中，我们在使用交换门的幼稚方法中实现了该状态的三倍，与raussendorf [phys的方案相当，及时使用。 Rev. A 72，052301（2005）]，需要动态控制。我们还通过使用哈密顿人的纠缠能力的结果来证明国家逆转的下限，并表明我们在最短时间的$ 1.502（1+1/n）$之内。我们的下边界适用于所有最近的邻居Q Qubit协议，该协议具有任意有限的Ancilla空间，本地操作和经典交流。最后，我们将我们的方案扩展到一个无限的邻居，与时间无关的汉密尔顿方案，用于国家逆转。这包括具有几乎均匀耦合的链，对于实验实施可能特别可行。
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.
