Program
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SESSION 6: Superconducting qubitsChair: (Seth Merkel (HRL Laboratories)) | |
| 8:30am-9:15am | Steven Girvin, Yale University Schroedinger's cat meets Maxwell's demon: Quantum error correction (that works) | Abstract. Successful quantum error correction requires construction of a quantum "Maxwell's demon" which can remove the entropy generated by errors in the N physical qubits comprising a logical qubit, without learning (and therefore destroying) the quantum information stored in the logical qubit. Because N physical qubits have an error rate N times larger than a single physical qubit, the Maxwell demon must be sufficiently fast and accurate to overcome this factor of N just to reach the 'break-even' point where the lifetime of the quantum information begins to be enhanced. Experiments at Yale have successfully demonstrated quantum error correction that reaches the break-even point for the first time. In addition, recent experiments have demonstrated entanglement between logically encoded qubits. Paradoxically, these successes were achieved by storing the quantum information in objects that are normally considered quite fragile, namely 'Schoedinger cat' states of photons. Elementary: [1] Wiring up quantum systems, R.J. Schoelkopf and S.M. Girvin, Nature 451, 664 (2008). [2] Superconducting Circuits for Quantum Information: An Outlook, M.H. Devoret and R.J. Schoelkopf, Science 339, 1169 (2013). Advanced: [3] Deterministically encoding quantum information in 100-photon Schoedinger cat states, Vlastakis, B., et al. Science 342, 607 (2013). [4] A Schroedinger Cat Living in Two Boxes, Chen Wang, et al., Science 352, 1087 (2016). [5] Extending the lifetime of a quantum bit with error correction in superconducting circuits, Nissim Ofek, et al., Nature 536, 441445 (2016). [6] A CNOT gate between multiphoton qubits encoded in two cavities, Serge Rosenblum, et al., arXiv:1709.05425. |
| 9:15am-9:45am | Juan Atalaya, University of California, Riverside Correlators in continuous measurement of non-commuting qubit observables and their applications | Abstract. There has been a rapid experimental progress in continuous quantum measurement of superconducting qubits, including simultaneous measurement of non-commuting observables. In this talk, we focus on temporal correlations of the noisy measurement outputs and discuss the theory for the correlators, comparison with experiment, and applications in parameter estimation and quantum error correction. First, using the quantum Bayesian formalism, we derive analytics for the correlators in simultaneous measurement of two non-commuting observables of a qubit. The theory agrees with experiment very well. Moreover, the correlators can be used for an ultrasensitive estimation of residual Rabi oscillations. Next, we derive a general theoretical result for multi-time correlators in measurement of several non-commuting observables. Surprisingly, we find that for a unital evolution in the absence of phase backaction from measurement, the N-time correlators factorize into a product of two-time correlators for even N. For odd N, a similar factorization also includes the average signal at the earliest time. Experimental results for N=3 and N=4 with two non-commuting measurement channels show a good agreement with this prediction. Finally, we discuss application of the theoretical results for correlators in the error analysis for the 4-qubit Bacon-Shor code, operating with continuous measurement of non-commuting gauge operators. |
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SQuInT Chief Organizer
Akimasa Miyake, Assistant Professor
amiyake@unm.edu
SQuInT Co-Organizer
Mark M. Wilde, Assistant Professor LSU
mwilde@phys.lsu.edu
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Gloria Cordova
gjcordo1@unm.edu
505 277-1850
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Ivan Deutsch, Regents' Professor
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