



@article {2556,
	title = {Nearly optimal time-independent reversal of a spin chain},
	journal = {accepted for publication in Physical Review Research},
	year = {2020},
	month = {3/5/2020},
	abstract = {<p>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.\&nbsp;</p>},
	url = {https://arxiv.org/abs/2003.02843},
	author = {Aniruddha Bapat and Eddie Schoute and Alexey V. Gorshkov and Andrew M. Childs}
}
