I am a Staff Researcher at the Institute for Quantum Computing at Baidu Research. At Baidu Quantum, I focus on the research on quantum computing and the development of Baidu Quantum Platform. In particular, I lead the development of Paddle Quantum, a Python library for quantum machine learning. My research investigates a broad range of perspectives of quantum computing and quantum information, including quantum communication, entanglement theory, near-term quantum applications, quantum machine learning, and quantum control. I am also an editor of Quantum.

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 in 2018 (Chancellor’s List for Outstanding Thesis), 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 arXiv. My full CV is available *here*.

** Hiring**: We are looking for

- Quantum Information
- Quantum Computation
- Machine Learning
- Optimization
- Quantum Control
- Quantum Programming

PhD in Quantum Information, 2018

University of Technology Sydney

BSc in Mathematics, 2014

Sichuan University

- 2021.08, our work “LOCCNet” on exploring distributed quantum information processing protocols with machine learning was accepted as a talk at AQIS 2021. Discover novel improved LOCC protocols for entanglement distillation. The module was available on Paddle Quantum (a quantum machine learning toolkit).
- 2021.08, our work Variational Quantum Algorithms for Trace Distance and Fidelity Estimation was accepted as a talk at AQIS 2021.
- 2021.08, our work Noise-Assisted Quantum Autoencoder was accepted as a talk at AQIS 2021.
- 2021.08, our work A Hybrid Quantum-Classical Hamiltonian Learning Algorithm was accepted as a talk at AQIS 2021.
- 2021.08, our work Symmetric distinguishability as a quantum resource was published in New Journal of Physics and accepted as a talk at AQIS 2021.
- 2021.06, our paper “Variational Quantum Singular Value Decomposition” was published in Quantum.
- 2021.06, I was invited to serve as a
*program committee member*for AQIS 2021. - 2021.05, our work “Measurement Error Mitigation via Truncated Neumann Series” [arXiv] (with my colleagues Kun Wang and Yu-Ao Chen) was accepted as a talk at TQC 2021.
- 2021.05, our work “Bounding the forward classical capacity of bipartite quantum channels” arXiv was accepted by TQC 2021.
- 2021.03, new paper “Lower bound the T-count via unitary stabilizer nullity” [arXiv] with our research intern Jiaqing Jiang.
- 2020.12, new paper “Detecting and quantifying entanglement on near-term quantum devices” [arXiv]. Methods for computing Logarithmic Negativity on NISQ devices.
- 2020.12, new paper “Physical Implementability of Quantum Maps and Its Application in Error Mitigation” with Jiaqing Jiang and Kun Wang [arXiv].
- 2020.12, I gave an invited talk on Entanglement Cost (Quantum Information Seminar) at Shaanxi Normal University [slides].
- 2020.12, our paper “VSQL: Variational Shadow Quantum Learning for Classification” (with my visiting/intern students Guangxi and Zhixin) was accepted to AAAI 2021. It is now available on arXiv.
- 2020.12, I will give an invited talk on Near-term Quantum Algorithms for Quantum Information at Workshop on Quantum Computing and Quantum Information organized by Institute of Physics CAS.
- 2020.12, I will give an invited talk on Entanglement Theory at AMSS-UTS Joint Workshop on Quantum Computing organized by AMSS CAS and UTS.
- 2020.11, I gave a contributed talk on Quantum Communication [slides] at Beyond IID Workshop 2020.
- 2020.09, I am invited to serve as a
*program committee member*for Beyond IID Workshop 2020. - 2020.08, I am now an
**Editor**of Quantum. Submissions are welcome! - 2020.07, I gave an invited talk on
*Variational quantum algorithms for state preparation and matrix decomposition*at the Innovation Salon organized by Peng Cheng Laboratory [slides]. - 2020.07, our work
*Cost of quantum entanglement simplified*has been published in**Physical Review Letters**. See news on phys.org for more information. - 2020.06, I gave an
**invited keynote**on*Quantum Channel’s Resource Theory*[slides] at**TQC 2020**. - 2020.06, I gave a contributed talk
*Optimizing the fundamental limits for quantum and private communication*[arXiv] [slides] at**TQC 2020**. We establish improved upper bounds on the quantum and private capacities of depolarizing channel, generalized amplitude damping channel, and BB84 channel. - 2020.06, new paper “More Practical and Adaptive Algorithms for Online Quantum State Learning” with my intern student Yifang Chen [arXiv].
- 2020.05, new paper “Variational quantum Gibbs state preparation with a truncated Taylor series” with my visiting students Youle Wang and Guangxi Li [arXiv].
- 2020.04, our paper
*Quantification of Unextendible Entanglement and Its Applications in Entanglement Distillation*was accepted by**ISIT 2020**. - 2020.02, new paper
*Quantum algorithms for hedging and the Sparsitron*with Y. Hamoudi, M. Ray, P. Rebentrost, M. Santha, and S. Yang is available [arXiv]. - 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**. - 2019.09, 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**.

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 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, 2018 [link]. (**QIP 2017 talk**).**X. Wang**, K. Fang, and R. Duan, “*Semidefinite programming converse bounds for quantum communication*,” IEEE Transactions on Information Theory, 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, 2019 [link]. (**QIP 2018 talk**).

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, 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:

**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**).**X. Wang**and M. M. Wilde, “*Cost of quantum entanglement simplified*,” Physical Review Letters, 2020 [link]. Check “Healing an Achilles’ heel of quantum entanglement ” at phys.org for more details.

Notably, the above 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.

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, 2020 [link], (**AQIS 2019 long talk**).**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**).

Quantum resource theory (QRT) offers a powerful framework for studying different phenomena in quantum physics. It aims to capture and quantify the desirable quantum effect, and optimize its use for particular quantum applications. My interests in this area lie in the mathematical analysis and characterization of quantum resources, as well as the applications of QRT for other quantum technologies. Good examples of my results are as follows:

**X. Wang**and M. M. Wilde, “Resource theory of asymmetric distinguishability,” Physical Review Research, (**QIP 2020 talk**).

In particular, I was invited to deliver a keynote on *Quantum Channel’s Resource Theory* [slides] at **TQC 2020**.

heorythe 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).

- VSQL: Variational Shadow Quantum Learning for Classification

Guangxi Li, Zhixin Song, and**Xin Wang**

[AAAI 2021] - Noise-Assisted Quantum Autoencoder

Chenfeng Cao and**Xin Wang**

Presented at**AQIS 2021**as a talk

[PR Applied] - Pursuing the fundamental limits for quantum communication
**Xin Wang**

Presented at**TQC 2020**as a talk

[IEEE TIT] - Cost of quantum entanglement simplified
**Xin Wang**and Mark M. Wilde

[Physical Review Letters] - Variational Quantum Singular Value Decomposition
**Xin Wang**, Zhixin Song, and Youle Wang

Quantum - More Practical and Adaptive Algorithms for Online Quantum State Learning

Yifang Chen and**Xin Wang**

arXiv:2006.01013 - Variational quantum Gibbs state preparation with a truncated Taylor series

Youle Wang, Guangxi Li, and**Xin Wang**

arXiv:2005.08797 - Quantifying the magic of quantum channels
**Xin Wang**, Mark M. Wilde, Yuan Su

New Journal of Physics, 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).

[IEEE TIT][ISIT][arXiv] - Quantum algorithms for hedging and the Sparsitron

Yassine Hamoudi, Maharshi Ray, Patrick Rebentrost, Miklos Santha,**Xin Wang**, Siyi Yang

arXiv:2002.06003 - 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

Accepted by**ISIT 2020**as a talk.

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

Quantum (in press, 2020)

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].