Department of Physics, National University of Singapore
Condensed Matter Seminar Series
To receive email notifications of this seminar series, please send an email to zouliujun@gmail.com to request.
Condensed Matter Seminar Series
To receive email notifications of this seminar series, please send an email to zouliujun@gmail.com to request.
Upcoming Seminars
(Both online and in-person seminars will be broadcast via Zoom.)
(Click the upper right corner of this page to see the previous seminars and their recordings.)
The seminar series in the fall semester of 2025 is over, and the next seminar will take place in the spring semester of 2026.
Time: 9am, January 23 2026, GMT+8
Location: Online
Zoom: https://nus-sg.zoom.us/j/89156543585?pwd=wsrGn2Qs72kiMlqEb5zX7DDyWkcnP4.1
Password: 502120
Speaker: Vladimir Calvera
Title: Invariants for (2+1)D crystalline symmetry-protected topological phases
Abstract: I will present a set of many-body invariants that characterize bosonic symmetry-protected (SPT) phases in two spatial dimensions with symmetry $G = G_{\text{space}}\times K$, where $G_{\text{space}}$ is a wallpaper group and K= U(1), Z_n or SO(3) is an internal symmetry. These invariants are obtained from expectation values of partial rotation and reflections, combined with internal symmetries. In particular, I will show that `partial rotations' and `partial double reflections’ are sufficient to distinguish crystalline SPTs on the square and triangular lattices. I will also discuss how these invariants relate to topological effective actions and quantum numbers of lattice defects.
This talk is based on arXiv:2510.26074 (with Naren Manjunath and Maissam Barkeshli).
Time: 9am, January 30 2026, GMT+8
Location: Online
Zoom: https://nus-sg.zoom.us/j/89156543585?pwd=wsrGn2Qs72kiMlqEb5zX7DDyWkcnP4.1
Password: 502120
Speaker: Patrick Ledwith
Title: TBD
Abstract: TBD
Time: 9am, February 6 2026, GMT+8
Location: Online
Zoom: https://nus-sg.zoom.us/j/89156543585?pwd=wsrGn2Qs72kiMlqEb5zX7DDyWkcnP4.1
Password: 502120
Speaker: Richard Allen
Title: Quantum computing enhanced sensing
Abstract: Quantum computing and quantum sensing represent two distinct frontiers of quantum information science. In this work, we harness quantum computing to solve a fundamental and practically important sensing problem: the detection of weak oscillating fields with unknown strength and frequency. We present a quantum computing enhanced sensing protocol that outperforms all existing approaches. Furthermore, we prove our approach is optimal by establishing the Grover-Heisenberg limit — a fundamental lower bound on the minimum sensing time. The key idea is to robustly digitize the continuous, analog signal into a discrete operation, which is then integrated into a quantum algorithm. Our metrological gain originates from quantum computation, distinguishing our protocol from conventional sensing approaches. Indeed, we prove that broad classes of protocols based on quantum Fisher information, finite-lifetime quantum memory, or classical signal processing are strictly less powerful. Our protocol is compatible with multiple experimental platforms. We propose and analyze a proof-of-principle experiment using nitrogen-vacancy centers, where meaningful improvements are achievable using current technology. This work establishes quantum computation as a powerful new resource for advancing sensing capabilities.
There is no seminar during the week of February 16 2026 because of the Chinese Spring Festival.
There is no seminar during the week of February 23 2026 because it is the reading week at NUS.
There is no seminar during the week of March 30 2026 because of the Good Friday.
Time: 9am, March 6 2026, GMT+8
Location: Online
Zoom: https://nus-sg.zoom.us/j/89156543585?pwd=wsrGn2Qs72kiMlqEb5zX7DDyWkcnP4.1
Password: 502120
Speaker: Tyler Ellison
Title: Universal quantum computation with group surface codes
Abstract: The surface code is one of the leading approaches to building a fault-tolerant quantum computer. However, a central challenge for the surface code is implementing non-Clifford operations -- unitaries which map Pauli operators to non-Pauli operators. In this talk, I will introduce group surface codes, which are a natural generalization of the usual Z_2 surface code. I will show that group surface codes, for suitably chosen groups, can be leveraged to perform non-Clifford gates in the Z_2 surface code. Time permitting, I will describe three strategies for completing a universal gate set using group surface codes: through transversal non-Clifford gates, sliding surface codes, and magic state preparation. These strategies extend recent efforts in performing universal quantum computation in topological orders without the braiding of anyons. Moreover, they show how certain group surface codes allow us to bypass the restrictions set by the Bravyi-König theorem, which limits the computational power of topological Pauli stabilizer models.
This is work in progress with Vieri Mattei, Naren Manjunath, and Apoorv Tiwari.