CM Seminar - A review and recent progress in quantum error - mitigationonress in quantum error - mitigation

29 Apr2021

Speaker: Kristan Temme - IBM

Time: Apr 29, 2021 :: 10:00AM - 11:00AM



April 29, Thu 10am
Meeting ID: 641 8301 1430
Passcode: 113399

Speaker: Kristan Temme - IBM
Talk title: A review and recent progress in quantum error - mitigation

Abstract: Near-term applications of early quantum devices, such as quantum simulations, rely on accurate estimates of expectation values to become relevant. Decoherence and gate errors lead to wrong estimates. This problem was, at least in theory, remedied with the advent of quantum error correction. However, the overhead that is needed to implement a fully fault-tolerant gate set with current codes and current devices seems prohibitively large.  In turn, steady progress is made in improving the quality of the quantum hardware.  This leads to the question:  what computational tasks could be accomplished with only limited, or no error correction? In this talk we first review two simple techniques for quantum error mitigation that increase the quality of short-depth  quantum  simulations. The first method, extrapolation to the zero noise limit, subsequently cancels powers of the noise perturbations by an application of Richardson’s deferred approach to the limit. The second method cancels errors by resampling randomized circuits according to a quasi-probability distribution. The two schemes are presented and we will discuss their application in experiments. Furthermore we will discuss recent progress on applying error mitigation techniques to logical qubits that don't support a universal gate set  
and show how to implement encoded Clifford+T circuits. Here the Clifford gates are protected from noise by error correction while errors introduced by noisy encoded T-gates are mitigated using the quasi-probability method. As a result, Clifford+T circuits with a number of T-gates inversely proportional to the physical noise rate can be implemented on small error-corrected devices without magic state distillation. We argue that such circuits can be out of reach for state-of-the-art classical simulation algorithms. 

Short Bio: Kristan Temme is a Principal Research Staff Member and the manager of the Theory of Quantum Algorithms group at IBM's T.J. Watson Research Center. His research currently centers around quantum algorithms and noise in complex quantum systems with a focus on the applications of noisy intermediate scale quantum devices.

Kristan has received a diploma in Physics from the University of Heidelberg in 2007.  He completed his Ph.D in Physics at the University of Vienna in 2011 under the supervision of Frank Verstraete. During this time he studied quantum Markov processes and complex quantum many-body systems. Between 2012 and 2014 he was a postdoctoral fellow at the Massachusetts Institute of Technology. Between March 2014 and September 2015 Kristan held the IQIM postdoctoral Fellowship of the Gordon and Betty Moore Foundation at the California Institute of Technology. He joined IBM research in the fall of 2015.

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