One-Step Implementation of Two-Qubit Quantum Logic Gates

徐晶

Taoufik Said, A. Chouikh, Mohamed Bennai

Yun-Pil Shim, Jianjia Fei, Sangchul Oh +2 more

Any single-qubit unitary operation or quantum gate can be considered a rotation. Typical experimental implementations of single-qubit gates involve two or three fixed rotation axes, and up to three rotation steps. Here we show that, if the rotation axes can be tuned arbitrarily in a fixed plane, then two rotation steps are sufficient for implementing a single-qubit gate, and one rotation step is sufficient for implementing a state transformation. The results are relevant for "exchange-only" logical qubits encoded in three-spin blocks, which are important for universal quantum computation in decoherence free subsystems and subspaces.

Chun‐Ling Zhang, Mei Lu, Cheng-Li Luo +1 more

Abstract The quantum logic gate is a basic operation in quantum computing. SWAP gates are quite useful as a type of two-qubit logic gate. In this paper, we propose a fast scheme to get a deterministic SWAP gate between two atoms in just one step. In this scheme the experimental parameters, such as evolution time, laser parameters and so on, do not need to be controlled precisely. This greatly simplifies the actual operation. Meanwhile, the strict numerical simulations show that decoherence arising from spontaneous emission and cavity decay may be allowed to some extent. What is more, the idea can be used to generate a SWAP gate between two spatially separate atoms. It is worth noting that our scheme simplifies the complex steps found in some pre-existing schemes.

Christopher J. Ballance

Hai‐Rui Wei, Yao-Min Di, ZHANG-Jie

Optimal implementation of quantum gates is crucial for realization of quantum computation. We slightly modify the Khaneja-Glaser decomposition (KGD) for n-qubits and give a new Cartan subalgbra in the second step of the decomposition. Based on this modified KGD, we investigate the realization of three-qubit logic gate and obtain the result that a general three-qubit quantum logic gate can be implemented using at most 73 one-qubit gates rotations with respect to the y and z axes and 26 CNOT gates.