Xin Wang

Staff Researcher

Baidu Research

Biography

I am a Staff Researcher at the Institute for Quantum Computing at Baidu Research. I am interested in the theory of quantum information, quantum computing, quantum resource theories, and machine learning.

I was a Hartree Postdoctoral Fellow at the Joint Center for Quantum Information and Computer Science (QuICS) at the University of Maryland, College Park. I received my doctorate in quantum information from the University of Technology Sydney (UTS:QSI) in 2018, under the supervision of Prof. Runyao Duan and Prof. Andreas Winter. I obtained my B.S. in mathematics (with Wu Yuzhang Honor) from Sichuan University in 2014.

A full list of my publications can be found on Google Scholar or a rXiv. My full CV is available here.

Hiring: I am looking for self-motivated student interns who are interested in quantum computation and machine learning. Please feel free to contact me.

Interests

Quantum Information Theory
Quantum Computation
Quantum Resource Theories
Quantum Programming Language
Optimization and machine learning.

Education

PhD in Quantum Information, 2018
University of Technology Sydney
BSc in Mathematics, 2014
Sichuan University

Experience

Staff Researcher

Institute for Quantum Computing, Baidu Research

Jul 2019 – Present Beijing

Hartree Postdoctoral Fellow

QuICS, University of Maryland, College Park

Sep 2018 – Jul 2019 Maryland

News

2020.01, our work Efficiently computable bounds for magic state distillation has been accepted by Physical Review Letters.
2020.01, our work Quantifying the magic resources for quantum computation was presented as a talk at QIP 2020.
2020.01, our work Resource theory of asymmetric distinguishability was presented as a talk at QIP 2020.
2019.12, new paper Optimizing the fundamental limits for quantum and private communication is available [arXiv]. We establish improved upper bounds on the quantum and private capacities of depolarizing channel, generalized amplitude damping channel, and BB84 channel.
2019.11, our new paper Quantifying the unextendibility of entanglement is available online [arXiv].
2019.09, our paper Quantum Channel Simulation and the Channel’s Smooth Max-Information has been accepted by IEEE Transactions on Information Theory [paper].
2019.09, our paper Quantifying the magic of quantum channels has been published in New Journal of Physics [paper].
2019.09, our paper One-Shot Entanglement Distillation beyond LOCC has been published in New Journal of Physics [paper].
2019.06, our work Efficiently computable bounds for magic state distillation was presented as a long talk at AQIS 2019.
2019.06, our work Resource theory of asymmetric distinguishability will be presented as a talk at AQIS 2019.
2019.06, I am invited to deliver lectures and tutorials at the 2019 Illinois Quantum Computing Summer School.
2019.06, I am invited to serve as a program committee member for AQIS 2019.
2019.04, our paper Non-asymptotic entanglement distillation has been accepted by IEEE Transactions on Information Theory [paper].
2019.01, our work Entanglement cost of quantum state preparation and channel simulation was presented as a talk at QIP 2019 [slides][video].
2019.01, our paper On converse bounds for classical communication over quantum channels has been accepted by IEEE Transactions on Information Theory [paper].
2018.12, my PhD thesis “Semidefinite Optimization for Quantum Information” was awarded the Chancellor’s List for Best Thesis.
2018.10, our paper Using and reusing coherence to realize quantum processes was published in Quantum.
2018.10, our paper Semidefinite programming converse bounds for quantum communication was published in IEEE Transactions on Information Theory [link].

Featured Publications

The main focus of my research is to better understand the power and limits of information processing with quantum systems. I also aim to explore new applications of quantum information and new approaches to overcome theatrical challenges in realizing quantum technologies.

My Ph.D. thesis Semidefinite Optimization for Quantum Information (pdf) aims to contribute to the development of quantum Shannon theory, entanglement theory, and zero-error information theory. It explores the fundamental properties of quantum entanglement and establishes efficiently computable approximations for elementary tasks in quantum information theory by using semidefinite optimization, matrix analysis, and information measures.

QUANTUM SHANNON THEORY

Quantum Shannon theory is the study of the ultimate performance of communication with quantum systems. One of my primary topics is to investigate the communication capabilities of quantum channels under both finite blocklength and asymptotic regime. The asymptotic regime focuses on the ultimate limits of communication, while the finite blocklength regime focuses on a more practical scenario involving only small and medium number of bits or qubits. Good examples of my results in this area are as follows:

X. Wang, W. Xie, and R. Duan, “Semidefinite programming strong converse bounds for classical capacity,” IEEE Transactions on Information Theory, 64 (1), 640–653, 2018 [link]. (QIP 2017 talk).
X. Wang, K. Fang, and R. Duan, “Semidefinite programming converse bounds for quantum communication,” IEEE Transactions on Information Theory, 65 (4), 2583-2592, 2019 [link]. (QIP 2018 talk).
X. Wang, K. Fang, and M. Tomamichel, “On converse bounds for classical communication over quantum channels,” IEEE Transactions on Information Theory, 65 (7), 4609-4619, 2019 [link]. (QIP 2018 talk).

QUANTUM ENTANGLEMENT

Quantum entanglement is a key ingredient in many quantum information processing tasks, including teleportation, superdense coding, and quantum cryptography. I am interested in exploring the fundamental structure and the resource theory of entanglement. For example, I demonstrate the irreversibility of asymptotic entanglement manipulation under quantum operations that completely preserve the positivity of partial transpose (PPT), resolving a major open problem in quantum information theory.

X. Wang and R. Duan, “Irreversibility of Asymptotic Entanglement Manipulation Under Quantum Operations Completely Preserving Positivity of Partial Transpose,” Physical Review Letters, 119 (18), 180506, 2017 [link]. (QIP 2017 talk).

I also established single-letter formulas to efficiently quantify the quantum entanglement required for quantum state preparation and quantum channel implementation in the following paper:

X. Wang and M. M. Wilde, “Exact entanglement cost of quantum states and channels under PPT-preserving operations,” arXiv:1809.09592, [link]. (QIP 2019 talk).

Notably, this work introduces the first entanglement measure that is efficiently computable while possessing a direct operational meaning for general bipartite states, thus solving a question that has remained open since the inception of entanglement theory over two decades ago. This unique feature helps us better understand the fundamental structure and power of entanglement.

FAULT-TOLERANT QUANTUM COMPUTATION

Magic state manipulation is a crucial component in the leading approaches to realizing scalable, fault-tolerant, and universal quantum computation. Related to magic state manipulation is the resource theory of magic states, for which one of the goals is to characterize and quantify quantum “magic.” In the following two papers, we develop resource-theoretic approaches to study the non-stabilizer resources in fault-tolerant quantum computation. We, in particular, introduce efficiently computable magic measures to quantify the magic of quantum states as well as noisy quantum circuits and explore their applications in magic state distillation, gate synthesis, and classical simulation of noisy circuits.

X. Wang, M. M. Wilde, and Y. Su, “Efficiently computable bounds for magic state distillation,” Physical Review Letters (in press), 2020 [link].
X. Wang, M. M. Wilde, and Y. Su, “Quantifying the magic of quantum channels,” New Journal of Physics, 21 (10), 103002, 2019 [link]. (QIP 2020 talk).

ZERO-ERROR INFORMATION THEORY

While the ordinary Shannon theory studies communication with asymptotically vanishing errors, Shannon also investigated the information theory when errors are required to be strictly zero, which is known as the zero-error information theory. In this area, the communication problem reduces to the study of the so-called confusability graph (non-commutative graph) of a classical channel (quantum channel). A good example of my research in this area is proving the separation between the quantum Lovász number and the entanglement-assisted zero-error capacity:

X. Wang and R. Duan, “Separation Between Quantum Lovász Number and Entanglement-Assisted Zero-Error Classical Capacity,” IEEE Transactions on Information Theory, 64 (3), 1454–1460, 2018 [link]. (Contributed talk at AQIS 2017).

Publications

Quantifying the magic of quantum channels
Xin Wang, Mark M. Wilde, Yuan Su
Presented at QIP 2020 as a talk.
[NJP] [arXiv]
Resource theory of asymmetric distinguishability
Xin Wang and Mark M. Wilde
Presented at QIP 2020 as a talk.
Phys. Rev. Research 1, 033170, (2019)
[PRR][arXiv]
Quantum Channel Simulation and the Channel’s Smooth Max-Information
Kun Fang, Xin Wang, Marco Tomamichel, Mario Berta
Presented at ISIT 2018, TQC 2018 and BIID 2018 as contributed talks.
IEEE Transactions on Information Theory (in press, 2019).
[TIT][ISIT][arXiv]
Optimizing the fundamental limits for quantum and private communication
Xin Wang
arXiv:1912.00931
Resource theory of asymmetric distinguishability for quantum channels
Xin Wang and Mark M. Wilde
Phys. Rev. Research 1, 033169, (2019)
[PRR] [arXiv]
Quantifying the unextendibility of entanglement
Kun Wang, Xin Wang, and Mark M. Wilde
arXiv:1911.07433
Efficiently computable bounds for magic state distillation
Xin Wang, Mark M. Wilde, Yuan Su
Physical Review Letters (in press, 2020) Presented at AQIS 2019 as a long talk.
[PRL][arXiv]
Time-dependent Hamiltonian simulation with L1-norm scaling
Dominic W. Berry, Andrew M. Childs, Yuan Su, Xin Wang, Nathan Wiebe
arXiv:1906.07115
On converse bounds for classical communication over quantum channels
Xin Wang, Kun Fang, Marco Tomamichel
Presented at QIP 2018 as a contributed talk.
IEEE Transactions on Information Theory 65(7): 4609 - 4619 (2019).
[TIT][arXiv]
Exact entanglement cost of quantum states and channels under PPT-preserving operations
Xin Wang and Mark M. Wilde
Presented at QIP 2019 as a contributed talk.
[arXiv]
α-Logarithmic negativity
Xin Wang and Mark M. Wilde
arXiv:1904.10437
Resource theory of entanglement for bipartite quantum channels
Stefan Bäuml, Siddhartha Das, Xin Wang, Mark M. Wilde
arXiv:1907.04181
One-shot entanglement distillation beyond LOCC
Bartosz Regula, Kun Fang, Xin Wang, Mile Gu
New Journal of Physics 21, 103017 (2019)
[NJP][arXiv]
Non-asymptotic entanglement distillation
Kun Fang, Xin Wang, Marco Tomamichel, Runyao Duan
Presented at AQIS 2017 as a long talk.
IEEE Transactions on Information Theory 65(10): 6454 - 6465 (2019).
[TIT][arXiv]
Semidefinite programming converse bounds for quantum communication
Xin Wang, Kun Fang, Runyao Duan
Presented at QIP 2018 as a contributed talk.
IEEE Transactions on Information Theory 65(4): 2583 - 2592 (2019).
[TIT][arXiv][slides]
Separation between quantum Lovász number and entanglement-assisted zero-error capacity
Xin Wang and Runyao Duan
Presented at AQIS 2016 as a contributed talk.
IEEE Transactions on Information Theory 64(3):1454-1460 (2018).
[TIT][arXiv][slides]
Converse bounds for classical communication over quantum networks
Wei Xie, Xin Wang, and Runyao Duan
Proceedings of the 2018 IEEE International Symposium on Information Theory.
[ISIT][arXiv]
Probabilistic distillation of quantum coherence
Kun Fang, Xin Wang, Ludovico Lami, Bartosz Regula, Gerardo Adesso
Physical Review Letters 121, 070404 (2018).
[PRL][arXiv]
Gaussian quantum resource theories
Ludovico Lami, Bartosz Regula, Xin Wang, Rosanna Nichols, Andreas Winter, Gerardo Adesso
Physical Review A 98, 022335 (2018) (Editors’ Suggestion)
[PRA][arXiv]
One-shot coherence distillation
Bartosz Regula, Kun Fang, Xin Wang, Gerardo Adesso
Physical Review Letters 121, 010401 (2018).
[PRL][arXiv]
Semidefinite programming strong converse bounds for classical capacity
Xin Wang, Wei Xie, Runyao Duan
Presented at QIP 2017, ISIT 2017, BIID 2017 as contributed talks.
IEEE Transactions on Information Theory 64(1): 640-653 (2018).
[TIT][arXiv][slides]
Using and reusing coherence to realize quantum processes
María García Díaz, Kun Fang, Xin Wang, Matteo Rosati, Michalis Skotiniotis, John Calsamiglia, Andreas Winter
Quantum Journal 2, 100 (2018).
[Quantum][arXiv]
Q|SI⟩: A Quantum Programming Environment
Shusen Liu, Xin Wang, Li Zhou, Ji Guan, Yinan Li, Yang He, Runyao Duan, Mingsheng Ying
In Symposium on Real-Time and Hybrid Systems. Lecture Notes in Computer Science, vol 11180. Springer, Cham.
arXiv:1710.09500, software available at http://www.qcompiler.com.
Tripartite-to-bipartite Entanglement Transformation by Stochastic Local Operations and Classical Communication and the Classification of Matrix Spaces
Yinan Li, Youming Qiao, Xin Wang, Runyao Duan
Presented at AQIS 2016 as a contributed talk.
Communications in Mathematical Physics 358(2): 791–814 (2018).
[CMP][arXiv][slides]
Irreversibility of Asymptotic Entanglement Manipulation Under PPT operations
Xin Wang and Runyao Duan
Presented at QIP 2017 as a contributed talk and at AQIS 2017 as a long talk.
Physical Review Letters 119, 180506 (2017).
[PRL][arXiv][slides]
Approximate broadcasting of quantum correlations
Wei Xie, Kun Fang, Xin Wang, Runyao Duan
Physical Review A 96, 022302 (2017).
Presented at AQIS 2017.
[PRA][arXiv]
Indistinguishability of Quantum States by PPT operations in the many-copy scenario
Yinan Li, Xin Wang, Runyao Duan
Physical Review A 95, 052346 (2017).
[PRA][arXiv]
Rains’ bound is not additive
Xin Wang and Runyao Duan
Physical Review A 95, 062322 (2017).
[PRA][arXiv]
A semidefinite programming upper bound of quantum capacity
Xin Wang and Runyao Duan
Proceedings of the 2016 IEEE International Symposium on Information Theory.
[ISIT][arXiv]
On the quantum no-signalling assisted zero-error simulation cost of non-commutative bipartite graphs
Xin Wang and Runyao Duan
Proceedings of the 2016 IEEE International Symposium on Information Theory.
[ISIT][arXiv]
Improved Semidefinite Programming Upper Bound on Distillable Entanglement
Xin Wang and Runyao Duan
Presented at AQIS 2016 as a contributed talk.
Physical Review A 94, 050301 (Rapid communication) (2016).
[PRA][arXiv]
Activated zero-error capacity of quantum channels in the presence of quantum no-signalling correlations
Runyao Duan and Xin Wang
[arXiv].