David Rodriguez Perez

Autonomous error correction of a single logical qubit using two transmons

  1. Ziqian Li,
  2. Tanay Roy,
  3. David Rodriguez Perez,
  4. Kan-Heng Lee,
  5. Eliot Kapit,
  6. and David I. Schuster
Large-scale quantum computers will inevitably need quantum error correction to protect information against decoherence. Traditional error correction typically requires many qubits,
along with high-efficiency error syndrome measurement and real-time feedback. Autonomous quantum error correction (AQEC) instead uses steady-state bath engineering to perform the correction in a hardware-efficient manner. We realize an AQEC scheme, implemented with only two transmon qubits in a 2D scalable architecture, that actively corrects single-photon loss and passively suppresses low-frequency dephasing using six microwave drives. Compared to uncorrected encoding, factors of 2.0, 5.1, and 1.4 improvements are experimentally witnessed for the logical zero, one, and superposition states. Our results show the potential of implementing hardware-efficient AQEC to enhance the reliability of a transmon-based quantum information processor.
arxiv pdf

Error-divisible two-qubit gates

  1. David Rodriguez Perez,
  2. Paul Varosy,
  3. Ziqian Li,
  4. Tanay Roy,
  5. Eliot Kapit,
  6. and David Schuster
We introduce a simple, widely applicable formalism for designing „error-divisible“ two qubit gates: a quantum gate set where fractional rotations have proportionally reduced
error compared to the full entangling gate. In current noisy intermediate-scale quantum (NISQ) algorithms, performance is largely constrained by error proliferation at high circuit depths, of which two-qubit gate error is generally the dominant contribution. Further, in many hardware implementations, arbitrary two qubit rotations must be composed from multiple two-qubit stock gates, further increasing error. This work introduces a set of criteria, and example waveforms and protocols to satisfy them, using superconducting qubits with tunable couplers for constructing continuous gate sets with significantly reduced error for small-angle rotations. If implemented at scale, NISQ algorithm performance would be significantly improved by our error-divisible gate protocols.
arxiv pdf