---
tags: General
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# Welcome to QI/QC Lab!

In Summer 2023, group meetings will take place at 2 PM Pacific Time on Wednesdays in Academic Surge 2022 (for in-person attendees) or on Zoom (for remote attendees, see group Slack for link). All regular meetings are recorded and uploaded to our [meeting archive on Box](https://ucdavis.box.com/s/z59opqur7afki1pr7jrk8gf4e3fzrsop) and previously on [Dropbox](https://www.dropbox.com/sh/7bxd05m9jddb60e/AAD2iIW26W-vaNOiWDf59n4na?dl=0).

# Members

| Name | Institution | Program | Research interests |
| ------------ | ------------ | -------- | ------------------ |
| Isaac Kim | UC Davis | PI, CS/Physics | |
| Ian Lim | UC Davis | PhD, Physics (2019-present) | Field theory, Entanglement entropy, Holography, QEC |
| Guangqi Zhao | USYD | PhD, Physics (2021 - Present) | Quantum Error Correction |
| Zijian Song | UC Davis | PhD, Physics (2020-present) | Quantum Information, Quantum Many Body Systems
| Michael Ragone | UC Davis | PhD, Math (2018-present) | Quantum Many Body Systems, Quantum Information
| Sanchayan Dutta | UC Davis | PhD, Math (2021-present) | Quantum Error Correction, Algebraic and Geometric Topology, Operator Algebras, Computational Complexity
| Arkin Tikku | USYD | PhD |
| Jintae Kim | SKKU | Integrated Master & PhD, Physics (2018 - present) | Quantum Error Correction, Condensed Matter Theory, Tensor Network, Lattice Gauge theory
| Hyun-Soo Kim | UC Davis | PhD, Physics (2019-present); joint w/ [Complexity Sciences Center](https://csc.ucdavis.edu/Welcome.html) | Quantum Cellular Automata, Quantum Dynamical Systems, Information in Complex Systems

# Resources
* [Overview](https://www.dropbox.com/sh/uqkxwq8enyj8bcx/AABtgZS_zW7OXW8XjP1EtVXoa?dl=0)
* [Past Meetings](https://www.dropbox.com/sh/7bxd05m9jddb60e/AAD2iIW26W-vaNOiWDf59n4na?dl=0). Recordings shifted to [Box](https://ucdavis.box.com/s/z59opqur7afki1pr7jrk8gf4e3fzrsop).
* Quantum Error Correction
* [Notes](https://www.dropbox.com/sh/ckbf2oqd111qzh2/AADWOL6wYkVk7XqdhQ0mSIkAa?dl=0)
* Decoders
* Tutorials
* [Practical Decoding for Surface/Toric Code](https://www.dropbox.com/s/v1pymoj5nygtx0u/7-6-2022%20Practical%20Decoding%20for%20Toric%20Code.mp4?dl=0)
* [PyMatching](https://github.com/oscarhiggott/PyMatching): Minimum weight perfect matching decoder. Use this with [Stim](https://github.com/quantumlib/Stim)
* [Stim](https://github.com/quantumlib/Stim): An extremely efficient stabilizer simulator. Use this with [PyMatching](https://github.com/oscarhiggott/PyMatching).
* [BP+OSD](https://github.com/quantumgizmos/bp_osd): A very flexible decoder for LDPC codes; see [Paper](https://arxiv.org/abs/2005.07016) for details.
* [Entanglement Bootstrap Notes](https://www.dropbox.com/sh/xm428nkdv6d9awh/AADFT87AJUYrZ5aMuHe_7pAoa?dl=0)
* [NISQ Notes](https://www.dropbox.com/sh/1fq8rb4pfzcr8f9/AAAvVb8RsYP2ClZWOX10tArFa?dl=0)

# Current Projects

**Policies**

1. Hyperlink to an overleaf page if and only if it is an internal project.
2. Project description should be no more than two lines.

| People | Collaborators | Project | Category | Status|
| ------- | -| -------- | -------- | ---|
| Michael, Bruno | | Dimerization in a class of O(n)-invariant quantum spin chains | | Nearly done
| Arkin, Isaac | | [Circuit depth vs. long range entanglement at finite energy density](https://www.overleaf.com/project/60f77e2baff48672480a6199) | NISQ | Nearly done
| Evan, Isaac | |Efficient estimation of noise susceptibility of arbitrary quantum circuits | NISQ |
| Zijian, Isaac | |[Solvable model of many-body qubit recycling](https://www.overleaf.com/project/624fd8e95465383e4be0be5c) | NISQ |
|Guangqi, Isaac| |Robust test of topologically ordered time crystal | NISQ |
|Jintae, Isaac| |3D Cluster State Construction Using Multiple Phonon Emitters| QEC |
|Ian, Isaac | | Modular flow with quantum singular value transform | |
| Isaac | Guillaume Dauphinais (Xanadu)| Fault-tolerant preparation of magic states with GKP codes | QEC| Hiatus|
| Isaac | Daniel Ranard (MIT) | Efficient certification of short-range entanglement | NISQ/EB|
| Isaac | Dmitry Abanin (U. of Geneva) | Theory of influence matrix | | Hiatus|
| Isaac | Zhaoyi Li (Stanford), Patrick Hayden (Stanford) | Noise conversion technique via code concatenation | QEC|
| Isaac | Bowen Shi (UCSD) Li Gao (U. Houston) | Continuity of modular commutator | EB| Hiatus|
| Zijian | Guanyu Zhu (IBM) | Exotic boundaries and domain walls of 3D color code | | |

# Completed Projects
| People | Collaborators | Project | Category | Status|
| ------- | -| -------- | -------- | ---|
| Isaac | Sergey Bravyi (IBM), Robert Koenig (TUM), Alexander Kliesch (TUM)| [Adaptive constant-depth circuits for manipulating non-abelian anyons](https://arxiv.org/abs/2205.01933) |NISQ| Done|
| Ian, Isaac | Bowen Shi (UCSD), Yijian Zou (Stanford), Jonathan Sorce (Stanford)|Modular commutator in conformal field theory | EB | [preprint on arXiv](https://arxiv.org/abs/2206.00027), [published in PRL](https://doi.org/10.1103/PhysRevLett.129.260402)

# Group Presentations
Presentations by group members take place on the first meeting of every month. These presentations provide a more in-depth exploration and discussion of an individual group member's research. Food is provided for in-person attendees (courtesy of Isaac's startup funding)!

| Date | Presenter | Title|
| -|-|-|
|6/1/2022| Arkin | Circuit depth vs. Energy|
|7/6/2022|Evan | Averaged circuit eigenvalue sampling (ACES)|
|8/3/2022|Guangqi | Topologically Ordered Time Crystal in Toric code |
|9/7/2022| Ian | From Modular Hamiltonians to Holographic Probes|
|10/5/2022|Isaac | Switching between Z_{2k} Surface Codes|
|11/2/2022|Sanchayan | An Introduction to Homological Codes|
|2/1/2023|Zijian | Qubit recycling and the path counting problem |
|5/17/2023|Hyun-Soo| A Discussion of Quantum Cellular Automata|
|6/28/2023|Ian| A Quantum Algorithm for Modular Flow|
|9/6/2023|Zijian|TBD|
|10/10/2023|Isaac|Learning shallow quantum circuits|
|12/6/2023|Jintae|UV/IR Mixing in Topological Phases|

## Upcoming presentations

<!---
* ~~July 6, 2022: Isaac Kim. *Some thoughts on arbitrary state preparation*
Abstract: One of the leading approaches to Hamiltonian simulation is based on qubitization. The overall cost of the qubitization algorithm crucially depends on the cost of the subroutines called “prepare” and “select.” I will provide a brief overview of this approach and explain some speculative ideas to improve the efficiencies of these subroutines.~~
--->

## Past presentations
* February 1, 2023: Zijian Song. _Qubit recycling and the path counting problem._
Abstract: Recently, it was shown that the qudits used in circuits of a convolutional form can be reset unitarily, even without measurement. In the work arXiv: 2301.03725, we analyze the fidelity of this protocol for a family of quantum circuits and establish a connection between this problem and the path counting problem.
In this talk I’ll first introduce the random quantum circuit and the qubit recycling protocol. Then I’ll show how the calculation is connected to the path counting problem in the noiseless case. Finally I’ll discuss the general noisy cases and compare our resuI might try lt with the previous numerical work.
* November 2, 2022: Sanchayan Dutta. *An Introduction to Homological Codes with an Empahsis on Fourier and Poincaré Dualities. [Video recording](https://ucdavis.box.com/s/6zbdsu9zc7itkykffgcgwk76t98coejk) and [slides](https://ucdavis.box.com/s/goum23jfgepaixb20rwmkpqj3cocaigx).*
* October 5, 2022: Isaac Kim. *Switching between Z_{2k} Surface Codes.*
* September 14, 2022: Ian Lim. *From Modular Hamiltonians to Holographic Probes*. Abstract: For a subsystem of a quantum state, the modular Hamiltonian is an operator closely linked to the entanglement of that subsystem with the whole state. I will review some recent work (arXiv:2206.00027) around a related entanglement measure called the modular commutator in the context of conformal field theory (CFT). I will also present some ongoing work around a "modular flow" associated to the modular Hamiltonian, and its holographic interpretation.
* August 4, 2022: Guangqi Zhao. *Topologically Ordered Time Crystal in Toric code.* [Video recording](https://www.dropbox.com/l/spri/AABE9dZf4b-Mmd-97XrozRfruWABl7kYz7c) and [slides](https://www.dropbox.com/l/spri/AACjI8u84r1Jg6hXoHse-Fh_l_NH5K501yE).
* July 6, 2022: Evan Hockings. *Implementing averaged circuit eigenvalue sampling on the surface code*. [Video recording](https://ucdavis.zoom.us/recording/detail?meeting_id=qbCXRsvfQKGO%2Flf3KmUb4Q%3D%3D) and [slides](https://www.dropbox.com/scl/fi/boardhraqz0jrxj477697/ACES-overview-22-7-7.pptx?dl=0&rlkey=0d57kbjidskj5ek2nut5y1x29).
Abstract: Averaged circuitI might try eigenvalue sampling (ACES) is a recently introduced technique for scalably characterising the noise associated with Clifford circuits. One particularly promising application is the circuits that implement error-correcting codes such as the surface code, as detailed noise characterisation may be leveraged to improve decoders. ACES is able to characterise the noise associated with an arbitrarily large surface code in a constant number of experiments.
* June 1, 2022: [Arkin Tikku (circuit depth lower bound project).](https://www.dropbox.com/s/2y5ycwee4gklj3q/2022-1-6%20Group%20Meeting.mp4?dl=0)