Bulletin of the American Physical Society
APS March Meeting 2015
Volume 60, Number 1
Monday–Friday, March 2–6, 2015; San Antonio, Texas
Session D51: Invited Session: Towards a Scalable Superconducting Quantum Computer |
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Sponsoring Units: GQI DCMP Chair: Michel Devoret, Yale University Room: Grand Ballroom C1 |
Monday, March 2, 2015 2:30PM - 3:06PM |
D51.00001: The surface code: processing experimental data Invited Speaker: Austin Fowler The surface code requires only nearest neighbor interactions and fidelities above approximately 0.99, making it highly compatible with superconducting circuits. In this talk, I review the surface code, and highlight the challenges and available optimizations when classically processing the output of a 9-qubit slice of surface code. [Preview Abstract] |
Monday, March 2, 2015 3:06PM - 3:42PM |
D51.00002: Bit-flip error correction with superconducting Xmon qubits Invited Speaker: John Martinis One of the outstanding challenges of quantum computation has been the realization of scalable qubits with high fidelity for all necessary operations. Here I discuss the design of a linear chain of 9 superconducting Xmon qubits that allows initialization, single and two qubit gates, and fast repetitive and simultaneous measurement with fidelity in the 99\%-99.9\% range. This performance has allowed us to perform bit-flip error correction with 8 repetition cycles that leads to improved lifetime of the state. The use of error correction based on the surface code enables all errors, both data and measurement, to be corrected to 1st and 2nd order. [Preview Abstract] |
Monday, March 2, 2015 3:42PM - 4:18PM |
D51.00003: Detecting arbitrary quantum errors via stabilizer measurements Invited Speaker: Matthias Steffen Fault tolerant quantum computing requires error correction, which relies on the ability to extract information about the error that occurred rather than the states of the data qubits themselves. Stabilizer codes are an attractive solution to this problem in which the parity of the data qubits is measured with the aid of additional ancilla qubits, resulting in the ``stabilization'' of a specific quantum state. Here, we perform syndrome (or error) extraction and arbitrary error detection by using a 2x2 lattice of superconducting qubits and simultaneous quantum non-demolition stabilizer measurements. In this experiment one of the Bell states is stabilized, and any arbitrary single-qubit bit or phase error can be detected without destroying the stabilized Bell state. This lattice is a representative of a primitive tile for the surface code which is a promising approach towards quantum error correction. [Preview Abstract] |
Monday, March 2, 2015 4:18PM - 4:54PM |
D51.00004: Tracking a Quantum Error Syndrome in Real Time: Quantum Jumps of Photon Parity Invited Speaker: Robert Schoelkopf Dramatic progress has been made in the last decade and a half towards realizing solid-state systems for quantum information processing with superconducting quantum circuits. Artificial atoms (or qubits) based on Josephson junctions have improved their coherence times more than 100,000-fold, have been entangled, and used to perform simple quantum algorithms. The next challenge for the field is demonstrating quantum error correction that actually improves the lifetimes, a necessary step for building more complex systems. I will describe recent experiments with superconducting circuits, where we store quantum information in the form of Schrodinger cat states of a microwave cavity, containing up to 100 photons. Using an ancilla qubit, we then monitor the gradual death of these cats, photon by photon, by observing the first jumps of photon number parity. This represents the first continuous observation of a quantum error syndrome, and may enable new approaches to quantum information based on photonic qubits. The performance of this error-monitoring system and the prospects for reaching ``breakeven,'' where quantum error correction improves the lifetime of stored information, will be discussed. [Preview Abstract] |
Monday, March 2, 2015 4:54PM - 5:30PM |
D51.00005: Detecting bit-flip errors in a logical qubit using stabilizer measurements Invited Speaker: Diego Rist\`e Quantum data is susceptible to decoherence induced by the environment and to control errors. A future fault-tolerant quantum computer will use quantum error correction (QEC) to actively protect against both. In the smallest QEC codes, the information in one logical qubit is encoded in a two-dimensional subspace of a larger Hilbert space of multiple physical qubits. For each code, a set of non-demolition multi-qubit measurements, termed stabilizers, can discretize and signal physical qubit errors without collapsing the encoded information. Using a 5-qubit superconducting processor, we realize the two parity measurements comprising the stabilizers of the three-qubit repetition code protecting one logical qubit from physical bit-flip errors. We construct these stabilizers as parallelized indirect measurements using ancillary qubits, and evidence their non-demolition character by generating three-qubit entanglement from superposition states. We demonstrate stabilizer-based quantum error detection (QED) by subjecting a logical qubit in any initial state to bit-flip errors on its constituent three physical qubits. Crucially, and in contrast to previous QED implementations, this approach keeps the quantum information encoded at all times, meeting a fundamental requirement for fault tolerance. [Preview Abstract] |
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