Dear Quanta Group, This seminar may be of interest! Please let Janice Balzer (cc'd) or me know if you'd like to meet with the speaker as well. Best, Dirk ---------- Forwarded message --------- From: Janice L Balzer &lt;balzer(a)mit.edu&gt; Date: Sat, Feb 25, 2017 at 11:24 AM Subject: [OQE] OQE Seminar: Dr. Yi-Kai Liu, NIST -- Wednesday, March 1, 2017, 11:00 AM, Haus Room, 36-428 To: oqe &lt;oqe(a)mit.edu&gt; [image: image001.png] Dr. Yi-Kai Liu National Institute of Standards and Technology (NIST) Seminar: “Phase Retrieval Using Unitary 2-Designs, with Applications to Quantum Process Tomography” Wednesday, March 1, 2017 11:00 AM Haus Room, 36-428 Hosted by: Prof. Dirk Englund Abstract: We consider a variant of the phase retrieval problem, where vectors are replaced by unitary matrices, i.e., the unknown signal is a unitary matrix U, and the measurements consist of squared inner products |Tr(C*U)|^2 with unitary matrices C that are chosen by the observer. This problem has applications to quantum process tomography, when the unknown process is a unitary operation. We show that PhaseLift, a convex programming algorithm for phase retrieval, can be adapted to this matrix setting, using measurements that are sampled from unitary 4- and 2-designs. In the case of unitary 4-design measurements, we show that PhaseLift can reconstruct all unitary matrices, using a near-optimal number of measurements. This extends previous work on PhaseLift using spherical 4-designs. In the case of unitary 2-design measurements, we show that PhaseLift still works pretty well on average: it recovers almost all signals, up to a constant additive error, using a near-optimal number of measurements. These 2-design measurements are convenient for quantum process tomography, as they can be implemented via randomized benchmarking techniques. This is the first positive result on PhaseLift using 2-designs. (This is joint work with Shelby Kimmel.) Biography: Yi-Kai Liu is a computer scientist at the US National Institute of Standards and Technology (NIST), and a Fellow at the Joint Center for Quantum Information and Computer Science (QuICS) at the University of Maryland. He specializes in quantum computation and cryptography. He has worked on the design of tamper-resistant quantum devices, compressed sensing methods for quantum tomography, quantum algorithms based on wavelet transforms, and the computational complexity of quantum chemistry. He received his PhD in computer science at the University of California in San Diego in 2007, and was a postdoctoral researcher at Caltech and UC Berkeley until 2011, when he moved to NIST. -- You received this message because you are subscribed to the Google Groups "MIT Quantum Photonics" group. To unsubscribe from this group and stop receiving emails from it, send an email to QP-mit+unsubscribe(a)googlegroups.com. To post to this group, send email to QP-mit(a)googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/QP-mit/B23F31EA93341940A25C8F445C5ADCF6A3… <https://groups.google.com/d/msgid/QP-mit/B23F31EA93341940A25C8F445C5ADCF6A3EB1605%40OC11EXPO24.exchange.mit.edu?utm_medium=email&utm_source=footer> . For more options, visit https://groups.google.com/d/optout. _______________________________________________ OQE mailing list OQE(a)mit.edu http://mailman.mit.edu/mailman/listinfo/oqe -- You received this message because you are subscribed to the Google Groups "MIT Quantum Photonics" group. To unsubscribe from this group and stop receiving emails from it, send an email to QP-mit+unsubscribe(a)googlegroups.com. To post to this group, send email to QP-mit(a)googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/QP-mit/B23F31EA93341940A25C8F445C5ADCF6A3… . For more options, visit https://groups.google.com/d/optout. -- Dirk R. Englund Associate Professor of Electrical Engineering and Computer Science Massachusetts Institute of Technology 77 Massachusetts Avenue, Room 36-591 englund(a)mit.edu; (617) 324-7014; http://qplab.mit.edu _______________________________________________ qip mailing list qip(a)mit.edu http://mailman.mit.edu/mailman/listinfo/qip