## Yi-Kai LiuI am a staff scientist at the National Institute of Standards and Technology (NIST), in the Applied and Computational Mathematics Division. I am also a Fellow and adjunct professor at the NIST-UMD Joint Center for Quantum Information and Computer Science (QuICS). I do research on quantum computation and theoretical computer science, in particular, quantum algorithms and complexity, quantum state tomography, machine learning, and quantum cryptography. Previously I was a postdoc in Computer Science at UC Berkeley, and a postdoc at the Institute for Quantum Information at Caltech. I received a PhD in computer science from UC San Diego, and a BA in mathematics from Princeton. You can reach me via e-mail at:yi-kai.liu [at] nist [dot] gov or: yikailiu [at] umd [dot] eduor: yikailiu00 [at] gmail [dot] com
This page was last updated on: Jan. 10, 2019. ## AnnouncementsApply here for postdoc jobs at QuICS, at the University of Maryland. This includes the Hartree Postdoctoral Fellowship, which covers all areas of quantum information, as well as other postdoctoral positions, which may focus on specific topics. Applications are due on Dec. 1, 2018. Apply here for NRC postdoc jobs at NIST. (My research group is listed here.) Applications are due on Feb. 1 and Aug. 1 each year. For graduate admissions, please apply to the Computer Science and Physics Departments at the University of Maryland. ## Some Recent TalksQuantum System Tomography, ARO/LPS Workshop on Quantum Characterization, Verification and Validation (QCVV), July 2017. QuICS is hosting QCrypt 2016, the 6th International Conference on Quantum Cryptography, Sept. 12-16, 2016, in Washington, DC! Tamper-Resistant Cryptographic Hardware in the Isolated Qubits Model, QCrypt 2014. Universal Low-rank Matrix Recovery using Pauli Measurements, 2012. Low-rank Methods for Learning Quantum States (joint work with S. Becker, B. Brown, J. Eisert, S. T. Flammia and D. Gross), Workshop on Low-rank Methods for Large-scale Machine Learning, NIPS 2010. Preparing Lattice Superpositions on a Quantum Computer, Workshop on Post-Quantum Information Security, Joint Quantum Institute, Oct. 2010. N-representability is QMA-complete (joint work with M. Christandl and F. Verstraete), Workshop on Quantum Marginals and Density Matrices, Fields Institute, July 2009. Quantum Algorithms Using the Curvelet Transform, STOC 2009. ## News ArticlesS. P. Jordan and Y.-K. Liu, "Quantum Cryptanalysis: Shor, Grover, and Beyond," Y.-K. Liu, "Quantum information: Show, don't tell," C. Boutin, "Quantum Physics Could Make Secure, Single-Use Computer Memories Possible," ## Joint Research ProjectsNIST Quantum Information Program NIST Standards for Post-Quantum Cryptography Research projects at UMD: - Scalable Certification of Quantum Computing Devices and Networks (coming soon)
- Quantum Optimization, Machine Learning and Simulation (coming soon)
- Optimal Measurements for Scalable Quantum Technologies (2014-present)
## TeachingCS138 Computer Algorithms, Spring 2009 (a course on approximation algorithms for combinatorial optimization, at Caltech). ## Papers (or try the handy Arxiv listing)I. Roth, R. Kueng, S. Kimmel, Y.-K. Liu, D. Gross, J. Eisert, M. Kliesch, "Recovering quantum gates from few average gate fidelities," Z. Ji, Y.-K. Liu, F. Song, "Pseudorandom Quantum States," V. Dunjko, Y.-K. Liu, X. Wu, J. M. Taylor, "Super-polynomial separations for quantum-enhanced reinforcement learning," arXiv:1710.11160. R. Perlner, Y.-K. Liu, "Thermodynamic Analysis of Classical and Quantum Search Algorithms," arXiv:1709.10510. P. Bierhorst, E. Knill, S. Glancy, Y. Zhang, A. Mink, S. Jordan, A. Rommal, Y.-K. Liu, B. Christensen, S. W. Nam, M. J. Stevens, L. K. Shalm, "Experimentally Generated Randomness Certified by the Impossibility of Superluminal Signals," C. Shen, R. W. Heeres, P. Reinhold, L. Jiang, Y.-K. Liu, R. J. Schoelkopf, and L. Jiang, "Optimized Tomography of Continuous Variable Systems Using Excitation Counting," ~ ~ ~ ~ ~ ~ ~ S. Kimmel and Y.-K. Liu, "Phase Retrieval Using Unitary 2-Designs," F. Krahmer and Y.-K. Liu, "Phase Retrieval Without Small-Ball Probability Assumptions," - F. Krahmer and Y.-K. Liu, "Phase Retrieval Without Small-Ball Probability Assumptions: Stability and Uniqueness,"
*SampTA 2015*, pp.411-414, [link]. - F. Krahmer and Y.-K. Liu, "Phase Retrieval Without Small-Ball Probability Assumptions: Recovery Guarantees for PhaseLift,"
*SampTA 2015*, pp.622-626, [link].
Y.-K. Liu, "Privacy amplification in the isolated qubits model," Y.-K. Liu, "Single-shot security for one-time memories in the isolated qubits model," Y.-K. Liu, "Building One-Time Memories from Isolated Qubits,"
J. Conroy, S. T. Davis, J. Kubina, Y.-K. Liu, D. P. O’Leary and J. D Schlesinger, "Multilingual Summarization: Dimensionality Reduction and a Step Towards Optimal Term Coverage," S. T. Flammia, D. Gross, Y.-K. Liu and J. Eisert, "Quantum Tomography via Compressed Sensing: Error Bounds, Sample Complexity, and Efficient Estimators," A. Anandkumar, D. P. Foster, D. Hsu, S. M. Kakade and Y.-K. Liu, "A Spectral Algorithm for Latent Dirichlet Allocation," M. Ohliger, V. Nesme, D. Gross, Y.-K. Liu and J. Eisert, "Continuous-variable quantum compressed sensing," ArXiv:1111.0853. ~ ~ ~ ~ ~ ~ ~ A. D. Bookatz, S. P. Jordan, Y.-K. Liu and P. Wocjan, "Quantum nonexpander problem is quantum-Merlin-Arthur-complete," A. Ambainis, A. M. Childs and Y.-K. Liu, "Quantum property testing for bounded-degree graphs," S. T. Flammia and Y.-K. Liu, "Direct Fidelity Estimation from Few Pauli
Measurements," Y.-K. Liu, "Universal low-rank matrix recovery from Pauli
measurements," M. Cramer, M. B. Plenio, S. T. Flammia, R. Somma, D. Gross, S. D.
Bartlett, O. Landon-Cardinal, D. Poulin and Y.-K. Liu, "Efficient Quantum
State Tomography," O. Landon-Cardinal, Y.-K. Liu and D. Poulin, "Efficient Direct
Tomography for Matrix Product States,"
ArXiv:1002.4632. D. Gross, Y.-K. Liu, S.T. Flammia, S. Becker and J. Eisert, "Quantum
state tomography via compressed sensing," ~ ~ ~ ~ ~ ~ ~ Y.-K. Liu, "Quantum Algorithms Using the Curvelet Transform,"
Y.-K. Liu, "The Local Consistency Problem for Stoquastic and 1-D
Quantum Systems," submitted.
ArXiv:0712.1388. Y.-K. Liu, "The Complexity of the Consistency and N-representability
Problems for Quantum States," PhD thesis, Univ. of California, San Diego,
2007. ArXiv:0712.3041. Y.-K. Liu, M. Christandl and F. Verstraete, "N-representability is
QMA-complete," Y.-K. Liu, "Consistency of Local Density Matrices is QMA-complete,"
~ ~ ~ ~ ~ ~ ~ Y.-K. Liu, V. Lyubashevsky and D. Micciancio, "On Bounded Distance
Decoding for General Lattices," Y.-K. Liu, "Gibbs States and the Consistency of Local Density
Matrices," Arxiv preprint:
quant-ph/0603012.
K. Levchenko and Y.-K. Liu, "Counting Solutions of Polynomial Equations"
[pdf]. A. Blanc, Y.-K. Liu and A. Vahdat, "Designing Incentives for
Peer-to-Peer Routing," My undergraduate senior thesis: original version or revised version (Aug. 26, 2002). ## Useful LinksNIST: QuICS seminar / Math Division seminar / Crypto reading groupBerkeley: EECS Department Calendar / Theory seminars / Quantum reading group Caltech: IQI Seminars / Physics Research Conference / CS Theory Seminar / IST Seminars / Technique (campus guide) |