Universal quantum control of two-electron spin quantum bits using dynamic nuclear polarization

By S. Foletti, Hendrik Bluhm, D. Mahalu, V. Umansky, A. Yacoby. 2009

298 citations recorded by the source corpus.

One fundamental requirement for quantum computation is to carry out universal manipulations of quantum bits at rates much faster than the qubit’s rate of decoherence. Recently, fast gate operations have been demonstrated in logical spin qubits composed of two electron spins where the rapid exchange of the two electrons permits electrically controllable rotations around one axis of the qubit. However, universal control of the qubit requires arbitrary rotations around at least two axes. Here, we show that by subjecting each electron spin to a magnetic field of different magnitude, we achieve full quantum control of the two-electron logical spin qubit with nanosecond operation times. Using a single device, a magnetic-field gradient of several hundred millitesla is generated and sustained using dynamic nuclear polarization of the underlying Ga and As nuclei. Universal control of the two-electron qubit is then demonstrated using quantum state tomography. The presented technique provides the basis for single- and potentially multiple-qubit operations with gate times that approach the threshold required for quantum error correction. The spin state of two electrons in a double well is a promising qubit. Now, such qubits can be arbitrarily rotated around two different axes by applying a magnetic field of different magnitude to each electron. This can be done in nanoseconds, before the stored information is lost.

Subfields: Atomic and Molecular Physics, and Optics, Electrical and Electronic Engineering

View Paper: https://www.semanticscholar.org/paper/907250566a9e61c20ac29d012059894aa422919a

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In Atomic and Molecular Physics, and Optics

In Electrical and Electronic Engineering

Citations in the corpus

Universal Quantum Transducers Based on Surface Acoustic Waves (2015, background): “In the regime of interest, the dominant character of the qubit’s levels is j1i ≈ j⇓⇑i, j0i ≈ j⇑⇓i (or vice versa) [66] and the transition frequency is approximately ω0 ≈ 2Δ.”
High-fidelity entangling gate for double-quantum-dot spin qubits (2016, methodology): “Through dynamic nuclear polarization and feedback, we set gμBΔBz/h≈1 GHz in all experiments.(19,22) Here, g = −0.”
Ultrafast optical control of entanglement between two quantum-dot spins (2010, methodology): “This interaction has also been used in electrically defined QD”
Silicon quantum electronics (2012, background): “In addition, most S/T qubit implementations in GaAs have made use of a gradient of hyperfine field, ∆Bz, between the two dots to be able to control the qubit along two orthogonal axes in the S/T basis (Foletti et al., 2009).”