Bulletin of the American Physical Society
APS March Meeting 2013
Volume 58, Number 1
Monday–Friday, March 18–22, 2013; Baltimore, Maryland
Session T10: Invited Session: Superconducting Qubits |
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Sponsoring Units: GQI DCMP Chair: Matthias Steffen, IBM Room: 309 |
Thursday, March 21, 2013 8:00AM - 8:36AM |
T10.00001: A strand of a surface code fabric with superconducting qubits Invited Speaker: Jerry Chow Quantum error correction will be a necessary component towards realizing scalable quantum computers with physical qubits. Theoretically, it is possible to perform arbitrarily long computations so long as the error rate is below a threshold value. The two-dimensional surface code permits relatively high fault-tolerant thresholds at the $\sim 1 \%$ level, and only requires a latticed network of qubits with nearest-neighbor interactions. I will discuss our implementation of a sub-section of the larger fabric using three transmon qubits and two linking microwave resonators. We demonstrate high-fidelity control over the sub-section surface code strand, verified via quantum prcoess tomography and randomized benchmarking experiments. Our fixed-frequency qubit approach relies on the two-qubit cross-resonance microwave driving interaction, which is now one of many microwave-based entangling gate protocols. I will also discuss the prospects to scale to surface code plaquette level experiments. [Preview Abstract] |
Thursday, March 21, 2013 8:36AM - 9:12AM |
T10.00002: Recent progress of the fluxonium qubit Invited Speaker: Michel Devoret Superconducting artificial atoms are all based on the purely dispersive non-linearity of a Josephson tunnel junction, which provides anharmonicity for a microwave oscillator mode. In the fluxonium qubit [1], the microwave oscillator crucially involves a superinductor, built with a linear array of several tens of ``large'' Josephson junctions. As the flux threading the loop formed by the superinductor and the tunnel junction is swept from zero to half a flux quantum, the g-e transition frequency varies between a sweet spot around 10GHz and another sweet spot at a few hundreds of MHz. By optimizing the fabrication and parameters of this superinductor [2], we have eliminated spurious phase slips through the array, and ensured that its self-resonance frequency lies above the frequency of the qubit. The improved relaxation times of this multi-junction circuit are promising for the design of a novel mesoscopic artificial atom, in which large anharmonicity, long coherence times and fast coupling rate to a cavity bus would all be compatible.\\[4pt] [1] Manucharyan et al., Science 326, 113 (2009) and Phys. Rev. B 85, 024521 (2012).\\[0pt] [2] Masluk et al., Phys. Rev. Lett. 109, 137002 (2012). [Preview Abstract] |
Thursday, March 21, 2013 9:12AM - 9:48AM |
T10.00003: Are materials good enough for a superconducting quantum computer? Invited Speaker: John Martinis Recent developments of surface codes now place superconducting quantum computing at an important crossroad, where ``proof of concept'' experiments involving small numbers of qubits can be transitioned to more challenging and systematic approaches that could actually lead to building a quantum computer. Although the integrated circuit nature of these qubits helps with the design of a complex architecture and control system, it also presents a serious challenge for coherence since the quantum wavefunctions are in contact with a variety of materials defects. I will review both logic gate design and recent developments in coherence in superconducting qubits, and argue that state-of-the-art devices are now near the fault tolerant threshold. Future progress looks promising for fidelity ten times better than threshold, as needed for scalable quantum error correction and computation. [Preview Abstract] |
Thursday, March 21, 2013 9:48AM - 10:24AM |
T10.00004: Overhead considerations of surface codes Invited Speaker: Austin Fowler How big would a commercially relevant superconducting quantum computer making use of the surface code need to be? What is the simplest experiment required to conclusively demonstrate that arbitrarily reliable quantum computation is technologically feasible? In this talk, we discuss the current state-of-the-art of the surface code and answer these two questions according to the latest available results. We describe ongoing research to bring down the overhead associated with quantum computation. [Preview Abstract] |
Thursday, March 21, 2013 10:24AM - 11:00AM |
T10.00005: Scaling up with superconducting qubits Invited Speaker: Alexandre Blais There have been significant developments in the field of superconducting qubits since the first observation, almost 15 years ago, of coherent oscillations in a superconducting electrical circuit. One key number could summarize this progress: the coherence time. Indeed, this quantity has increased by about 5 orders of magnitude since the first experiments. Characterizing this progress with a single number is, however, too simplistic. It does not capture the many improvements that the field has witnessed and, in the same way, hides many of the challenges that lie ahead. Indeed, with many ingredients having to come together and work just right, quantum computation is about more than long coherence times. A much better (yet incomplete) measure is the error rate of single- and two-qubit logical gates. Recent experiments show this rate approaching the level required for fault-tolerant quantum computation, a requirement for a scalable quantum computer architecture. In parallel, much effort has been invested in using superconducting qubits as artificial atoms to explore quantum optics with microwaves and in unconventional parameter ranges. With an emphasis on theoretical work, in this talk I will present an overview of the recent achievements in the field and present some challenges that will have to be overcome. [Preview Abstract] |
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