4 nuclear-spin states coherent manipulation
Franck Balestro
Tue, Jan. 12th 2016, 14:30-15:30

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Quantum control of individual spins in condensed-matter devices is a research field with a wide range of applications, from nano-spintronics to quantum information processing. If electron, possessing spin and orbital degrees of freedom, is conventionally used as the carrier of quantum information, alternative concepts propose nuclear spins as the building blocks for quantum computing[1], because they are naturally extremely well isolated from the environment, hence, less prone to decoherence. Recent advances in addressing isolated nuclear spins have opened up a path toward using nuclear-spin–based quantum bits, and an all electrical quantum coherent manipulation and read-out was experimentally demonstrated using Single Molecular Magnet (SMM) spin based transistor[2,3]

It was already suggested by Kane[1] that DC Stark effect of the hyperfine coupling could be used to tune different 31P nuclear spins in and out of resonance using local DC gate voltages. He, therefore, established the individual addressability by applying only a global microwave field. Our approach can be viewed as the extension of Kane’s proposal to AC gate voltages. We demonstrated coherent nuclear spin qubit manipulations using the hyperfine Stark effect to transform local electric fields into effective AC magnetic fields allowing us to show coherence time T2 = 400 microsecondes, Rabi frequency up to 10MHz and figure of merit up to 4000 for the three different nuclear spin qubits. Using this ability to fully coherently control the different qubits, we now perform Hadamard gate, mandatory step to perform the Grover algorithm.

[1] Kane, B. E. A silicon-based nuclear spin quantum computer. Nature 393, 133 (1998).

[2] Vincent, R. et al. Electronic read-out of a single nuclear spin using a molecular spin transistor. Nature 488, 357 (2012).

[3] Thiele, S. et al. Electrically driven nuclear spin resonance in single-molecule magnets. Science 344, 1135 (2014).

Contact : Michel BENINI


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