A programmable two-qubit quantum processor in silicon

By T. Watson, S. Phillips, E. Kawakami, D. Ward, P. Scarlino, Menno Veldhorst, D. Savage, Max G. Lagally, M. Friesen, Susan N. Coppersmith and 2 more. Nature, 2017

702 citations recorded by the source corpus.

Now that it is possible to achieve measurement and control fidelities for individual quantum bits (qubits) above the threshold for fault tolerance, attention is moving towards the difficult task of scaling up the number of physical qubits to the large numbers that are needed for fault-tolerant quantum computing. In this context, quantum-dot-based spin qubits could have substantial advantages over other types of qubit owing to their potential for all-electrical operation and ability to be integrated at high density onto an industrial platform. Initialization, readout and single- and two-qubit gates have been demonstrated in various quantum-dot-based qubit representations. However, as seen with small-scale demonstrations of quantum computers using other types of qubit, combining these elements leads to challenges related to qubit crosstalk, state leakage, calibration and control hardware. Here we overcome these challenges by using carefully designed control techniques to demonstrate a programmable two-qubit quantum processor in a silicon device that can perform the Deutsch–Josza algorithm and the Grover search algorithm—canonical examples of quantum algorithms that outperform their classical analogues. We characterize the entanglement in our processor by using quantum-state tomography of Bell states, measuring state fidelities of 85–89 per cent and concurrences of 73–82 per cent. These results pave the way for larger-scale quantum computers that use spins confined to quantum dots.

Subfields: Artificial Intelligence, Atomic and Molecular Physics, and Optics

View Paper: https://www.semanticscholar.org/paper/fbca19c57d65001bb6dddbe53ad9b08efd6aa882

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In Artificial Intelligence

In Atomic and Molecular Physics, and Optics

Citations in the corpus

Review of performance metrics of spin qubits in gated semiconducting nanostructures (2021, background): “[256, 264, 284] could be acknowledged to have reached the “processor” level, and only in the most recent one the fidelities where high enough to run the most elementary quantum circuits.”
A hole spin qubit in a fin field-effect transistor above 4 kelvin (2021, methodology): “The data were taken on resonance with a τ -dependent phase φ(τ), which adds an artificial oscillation [50].”
Qubits made by advanced semiconductor manufacturing (2021, background): “9% [9, 22] as well as two-qubit gates [8, 11, 23–25], algorithms [10], conditional teleportation [26], three-qubit entanglement [27] and four-qubit universal control [28] have already been demonstrated.”
Single artificial atoms in silicon emitting at telecom wavelengths (2020, background): “Siliconbased electrical qubits associated either to individual dopants [1] or to gate-defined quantum dots [2, 3], have already been used to demonstrate the elementary building blocks towards scalable integrated quantum circuits.”
Characterization and Compact Modeling of Nanometer CMOS Transistors at Deep-Cryogenic Temperatures (2018, background): “State-of-the-art quantum processors typically consist of a few qubits that are controlled and read out by general-purpose electronics operating at room-temperature [6]–[8].”