Perfect swap and transfer of arbitrary quantum states

Robert Mereau, David L. Feder

S. Salimi, S. Ghoraishipour, A. Sorouri

Keng Wah Choo, L. C. Kwek

We studied the use of quantum dots as a resource for teleportation and investigated how entanglement of the resource would affect the average fidelity of such a process. We then identified a suitable magnetic field, interdot distance, and the temperature to be used to achieve an average fidelity beyond the limit of the classical communication channel. We also explored the effects of decoherence on the teleportation process. We then investigated the state transfer or swapping between two quantum dots. We found that perfect quantum swap is possible in this system. A smaller magnetic field and interdot distance shortened the perfect state transfer time. Finally, we report on the performance of the system under different decoherence models.

Rachel Elizabeth Bachman, Eric Fredette, Jessica Fuller +4 more

We prove new results on perfect state transfer of quantum walks on quotient graphs. Since a graph G has perfect state transfer if and only if its quotient G/\pi, under any equitable partition \pi, has perfect state transfer, we exhibit graphs with perfect state transfer between two vertices but which lack automorphism swapping them. This answers a question of Godsil (Discrete Mathematics 312(1):129-147, 2011). We also show that the Cartesian product of quotient graphs \Box_{k} G_{k}/\pi_{k} is isomorphic to the quotient graph \Box_{k} G_{k}/\pi, for some equitable partition \pi. This provides an algebraic description of a construction due to Feder (Physical Review Letters 97, 180502, 2006) which is based on many-boson quantum walk.

Bahman Ahmadi, Mohammad Hassan Shirdareh Haghighi, Ahmad Mokhtar

Matthew Wampler, Nigel R. Cooper

We show how two many-body, generally mixed, quantum states can be swapped via collective, all-to-all interactions. Specifically, we present an experimentally relevant implementation for quantum dots that enables coherent exchange of quantum information between different species of nuclear spins, effectively achieving a perfect swap gate for qudits formed from these different species. This process also serves as a tool for nuclear spin purification. The results are obtained by mapping the problem onto perfect state transfer on a 1D chain. In the partially polarized limit, we demonstrate that the states can be exchanged independently of the initial state. We also assess the robustness of the procedure to decoherence and errors.