Optimising gates with a hybrid quantum-classical scheme
Performing a quantum computing task requires precise level of control to initialize, perform and measure the quantum system. With increasing size of the quantum processor the challenge is to maintain optimal control. Jun Li et.al. [Phys. Rev. Lett. 118, 150503 (2017) ] noted that one can drive a system from an initial state to a desired final state by using a hybrid scheme which performs the classically demanding part of a gradient search algorithm on a quantum computer. This technique was further demonstrated in [Npj Quantum Inf. 3, 45 (2017), Phys. Rev. A 98, 052341 ]. State-to-state transfer gates are sufficient for most of the quantum computing task, but, a universal quantum information implementation requires state independent gates. The techniques used in optimizing state-to-state gates can be modified to optimize for a state independent gate. I will talk about this method and show that it scales polynomially with the number of qubits and is general in terms of its implementation. Later, I will talk about how we can reduce the resource requirements even more using an NMR-related implementation and show some recent experimental results.
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