Bobby Antonio, Sougato Bose
It is known that it is possible to encode a logical qubit over many physical qubits such that it is immune to the effects of collective decoherence, and it is possible to perform universal quantum computation using these `decoherence-free' qubits. However, current proposed methods of performing gates on these encoded qubits could be difficult to implement, or could take too much time to perform. Here we investigate whether exploiting ring-exchange interactions, which may be naturally present, can simplify the implementation of these gates in any way. Using a ring exchange interaction, we have found a way to create a controlled-Z gate on the 4-site decoherence-free subspace and the 3-site decoherence-free subsystem, with high fidelity. The 4-site gate has interactions which are simpler than existing proposals, and the 3-site gate is also feasible although not necessarily an improvement on existing 3-site gates. We also investigate how timing errors and magnetic field fluctuations affect the fidelity of these gates.
View original:
http://arxiv.org/abs/1301.2922
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