Theoretical Physics · Open Quantum Systems

Tommy Chin

PhD Candidate in Physics

Institute for Gravitation & the Cosmos, The Pennsylvania State University

Every real quantum system leaks information into surroundings no experiment can fully measure. I work out how much of the whole a physicist can still infer from the part that stays accessible.

I will defend in May 2028 and am applying during the 2027 cycle for Fall 2028 postdoctoral positions in open quantum systems.

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Tommy Chin

Research

I work with Prof. Sarah Shandera on a framework for observers inside a quantum system who control neither the initial state, the dynamics, nor where the boundary between system and environment falls. The setting spans qubit networks, adaptive circuits, and spin chains.

I compute symbolically in Mathematica and run GPU-accelerated density-matrix simulations in Python on HTCondor clusters.

Publications

A fully connected N-qubit network partitioned into four open subsystems, each described by a reduced density matrix.

2026 · Preprint

Excitation Flow, Positivity, and Fisher Information for Open Subsystems of an N-Qubit Network

T. Chin, S. Shandera

arXiv:2605.15036 [quant-ph] (2026) · In revision for Physical Review A

I derive closed-form propagators for every K-qubit subsystem of a homogeneous all-to-all N-qubit network carrying a single conserved excitation. The direction of excitation flow fixes whether a propagator stays positive, and in this network positivity and complete positivity coincide. Decomposing the quantum Fisher information then separates state information from process information in a local measurement.

arXiv
Eigenvalue distribution in the unit disk for a non-phase-covariant qubit ensemble.

2024 · Peer-reviewed

Effective Dynamics of Qubit Networks via Phase-Covariant Quantum Ensembles

S. Prudhoe, U. Akhouri, T. Chin, S. Shandera

Open Systems & Information Dynamics 31, 2450016 (2024)

Splitting a closed system into subsystems yields an ensemble of open-system maps, one for each subsystem. We computed exact single-spin maps in small XXZ networks, then used the average map and its fluctuations to generate ensembles of arbitrary size. I computed the eigenvalue spectra and found that one phase-covariance-breaking parameter pushes a significant number of eigenvalues onto the real axis, recovering structure from general random-channel ensembles.

DOI arXiv
A 3 by 3 array of cubes showing strain and dark-state orientation configurations for silicon-vacancy centers.

2026 · Preprint

Impact of Strain and Dark States on Spectroscopic Measurements of Silicon-Vacancy Centers in Diamond

T. Chin, K. V. Narayan, I. Bashir, K. M. Bates, L. G. Stanton, E. Khatami, C. L. Smallwood

arXiv:2608.11168 [quant-ph] (2026) · Submitted to Physical Review B

Strain shifts and broadens the optical lines of silicon-vacancy centers, and dark states remove emitters from a spectrum altogether. I constructed five strain distribution models and built the GPU Monte Carlo pipeline behind this joint theory and experiment study. We compare the simulated spectra against heterodyne-detected and photoluminescence-detected measurements.

arXiv

Selected Talks

Honors & Awards

Teaching

Contact

Email: wjc5509@psu.edu

Office: 104 Davey Lab, Box 189, University Park, PA 16802

Institute for Gravitation & the Cosmos, Department of Physics, The Pennsylvania State University