The QUASAR End of Year Seminar will be held on Tuesday, December 9, 2025.

• Date: Tuesday, December 9, 2025
• Time: 10:25 AM-2:30 PM ET
• Location: STEM Complex

Below is the schedule and list of talks.

Time	Session
10:25 AM	Welcome & Opening Remarks
10:30 AM	Daniel Lovsted: Pauli-Based Computation in Plain and Secure Settings
11:00 AM	Kieran Mastel: The quantum smooth label cover problem is undecidable
11:45 AM	Lunch - Catered by Mad Radish
12:50 PM	Group Photo
1:00 PM	Bennett Hon: Nonlocal Games and Compact Quantum Groups
1:30 PM	Joshua Nevin: Noise-Robustness for Delegated Quantum Computation in the Circuit Model
2:15 PM	Closing Remarks

Talk 1: Daniel Lovsted

Pauli-Based Computation in Plain and Secure Settings

Pauli-based computation (PBC) is a measurement-based model of quantum computation introduced in 2016 by Bravyi, Smith, and Smolin. PBC excels at resource efficiency: in PBC, quantum resources (e.g., the size of the quantum register, the kinds of quantum operations performed) can be traded off for efficient classical processing. However, PBC is limited in that it yields only a sampling from the computation’s classical output distribution, as opposed to a fully general quantum output. PBC can be counterintuitive; the first part of this talk therefore aims to present PBC in an understandable way. Second, as PBC is well described as an interaction between a classical client and a quantum server, it is natural to investigate PBC in the context of blind quantum computing (BQC), which aims to provide cryptographic security in delegated settings. BQC, intersections between BQC and PBC, and ongoing work in this direction are discussed.

Talk 2: Kieran Mastel

The quantum smooth label cover problem is undecidable

In a recent work with Eric Culf, Connor Paddock, and Taro Spirig, we show that the quantum smooth label cover problem is RE-hard. This contrasts with the quantum unique label cover problem, which can be decided efficiently by Kempe, Regev, and Toner (FOCS’08). Our result aligns with the RE-hardness of the quantum label cover problem, which follows from the celebrated MIP* = RE result of Ji, Natarajan, Vidick, Wright, and Yuen (ACM’21). Additionally, we show that the quantum oracularized smooth label cover problem is also RE-hard. This aligns with the alternative quantum unique games conjecture on the RE-hardness of the quantum oracularized unique label cover problem proposed by Mousavi and Spirig (ITCS’25). Our techniques employ a series of reductions from the halting problem to the quantum smooth label cover problem, and include a quantum-sound version of Feige’s reduction from 3SAT to 3SAT5 (STOC’96), which may be of independent interest.

Talk 3: Bennett Hon

Nonlocal Games and Compact Quantum Groups

Recently, there has been growing evidence that quantum information systems exhibit symmetry phenomena that cannot be adequately captured by classical Lie groups. In the setting of nonlocal games, where the problem naturally admits a C*-algebraic formulation, it is therefore perhaps not surprising that quantized C*-algebras equipped with a Hopf structure (compact quantum groups) play a meaningful role. I will present a result of Mancinska and Roberson showing that perfect quantum strategies for the graph isomorphism game correspond exactly to quantum automorphisms of the underlying graphs. This connection involves orbitals of quantum permutation groups, which form a coherent configuration (generalized association scheme). Time permitting, I will also discuss some variations inspired by this framework.

Talk 4: Joshua Nevin

Noise-Robustness for Delegated Quantum Computation in the Circuit Model

In 2018, Broadbent devised an interactive proof protocol for verification of quantum computation between an almost-classical verifier V and a BQP prover P in which P has perfect hardware. This protocol makes use of the interleaving of computation rounds and test rounds, indistinguishable to the prover, where the outcomes of the test rounds are predetermined (to the verifier). In this work, we extend this idea by giving a simple statistical proof that a (slightly modified) multi-round run of the 2018 circuit-based protocol allows for verification of a quantum computation in the presence of noise in the hardware of P, with an improved upper bound on the noise toleration threshold compared to previous works on noise-robust delegated quantum computation. The proof technique for soundness in the 2018 paper also allows for a simple proof of security of the noise-robust protocol against an arbitrary deviating prover.