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This content will become publicly available on March 29, 2019

Title: A programmable two-qubit quantum processor in silicon

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 (1,2). 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 (3,4,5). Initialization, readout and single- and two-qubit gates have been demonstrated in various quantum-dot-based qubit representations (6,7,8,9). However, as seen with small-scale demonstrations of quantum computers using other types of qubit (10,11,12,13), combining these elements leads to challenges related to qubit crosstalk, state leakage, calibration and control hardware. 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. Thesemore » results pave the way for larger-scale quantum computers that use spins confined to quantum dots.« less
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  1. Delft Univ. of Technology (Netherlands). QuTech and the Kavli Inst. of Nanoscience
  2. Univ. of Wisconsin, Madison, WI (United States)
Publication Date:
Grant/Contract Number:
FG02-03ER46028; W911NF-17-1-0274; W911NF-12-1-0607; DMR-1121288; 676108
Accepted Manuscript
Journal Name:
Nature (London)
Additional Journal Information:
Journal Name: Nature (London); Journal Volume: 555; Journal Issue: 7698; Journal ID: ISSN 0028-0836
Nature Publishing Group
Research Org:
Univ. of Wisconsin, Madison, WI (United States). Materials Research Science and Engineering Center (MRSEC)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); US Army Research Office (ARO); National Science Foundation (NSF); Heiwa Nakajima Foundation; European Union (EU)-European Commission (EC). Marie Skłodowska-Curie actions (MSCA)
Country of Publication:
United States
77 NANOSCIENCE AND NANOTECHNOLOGY; 97 MATHEMATICS AND COMPUTING; quantum dots; quantum information; qubits
OSTI Identifier: