Research Interest

The hydrophobic effect is commonly summarized as “like dissolves like”. The usual explanation is that different forces hold polar vs nonpolar liquids together; molecules of hydrocarbons and other nonpolar compounds enjoy mutual attraction primarily via van der Waals interactions, whereas electrostatics dominate among polar species such as water. Thus, “oil and water don’t mix”, aggregating instead into separate liquid layers. This phase separation is routinely exploited in the purification and isolation of reaction products.

One long known outlier of this trend is the phase separation between perfluorocarbons and hydrocarbons. Both are nonpolar and hydrophobic in nature, but when perfluorinated alkanes (PFAS) and alkanes are mixed, they form separate hydrocarbon and “fluorous phase” layers. 

Despite extensive theoretical treatment, the origin of this behavior remains unclear. Here, we show that vibrational ground-state delocalization—via both zero-point energy shifts and mode-specific electrostatic coupling—selectively stabilizes CF4 dimers relative to CH4 and CH4···CF4. These quantum nuclear effects introduce an energetic bias ( 0.3 kcal/mol) that corresponds to 2kBT at 90 K, helping to resolve the long-standing phase separation anomaly.

MWTCC 2024 Talk

In 1939, Richard Feynman suggested that the dispersion forces on the nuclei of atoms in S states can be attributed to the attraction of each nucleus to its “own” charge distribution, polarized by correlation effects. In 1990, Hunt proved Feynman’s statement analytically within the polarization approximation.3 She also proved that the interpretation of dispersion forces generalizes to molecules of arbitrary symmetry. If one or both of the interacting molecules lack a center of symmetry, then the dipole moment induced by dispersion varies as R-6 in the separation between the centers of mass, as shown by Galatry and Hardisson4, while the dispersion force still varies as R-7. In this case, the rationale given by Feynman breaks down, yet Feynman’s explanation of the nature of dispersion forces on the nuclei still holds.

We have carried out ab initio calculations to probe the origins of the dispersion forces on the hydrogen nuclei in the H2 molecule in its lowest triplet state to determine whether Feynman’s interpretation still holds when exchange is included in the analysis.

Links to presentations/posters:

MWTCC 2023 Poster

Molecular hydrogen and other centrosymmetric diatomic species lack a permanent dipole, thus they are infrared inactive. In dense gasses, fly-by collisions of the species can create instantaneous dipoles, allowing for roto-vibrational transitions that are generally forbidden. This phenomena, known as collision induced absorption, allows for absorption in the infrared and microwave regions. 

In my research I perform advanced methods of computing the system's dipole, using finite field technique and spherical tensor analysis. With these techniques we are able to theoretically calculate the spectra of the pairs, to further probe astrophysical phenomena such as determining the temperatures of the planetary atmospheres of Jupiter or Saturn.

Currently I have run over 20,000 CCSD(T) calculations at 28 orientations and 24 intermolecular distances, and 36 bond lengths. These dipole values are fit to spherical harmonics to determine the tensor coefficients. The coefficients allow us to determine theoretical spectra and create 3D dipole surfaces such as the bottom left figure.

ACS Fall 2023 Poster 

We present a scalable, hardware-agnostic benchmarking protocol for quantum processors based on the action of Pauli operators on maximally entangled GHZ states. Unlike conventional methods such as randomized benchmarking (RB), quantum volume (QV), or cross-entropy benchmarking (XEB), the proposed approach eliminates the need for motion-reversal circuits, global inversions, or classical simulation of ideal outputs. 

Our protocol leverages the structural invariance of GHZ-like states under Pauli and Clifford conjugation, allowing each randomized layer to preserve the GHZ manifold while inducing measurable stochastic decay of coherence. This enables direct extraction of average error rates from measurement outcomes without tracking observables or performing post-processing. 

We develop the theoretical framework describing the bitwise action of Pauli operators on GHZ states, demonstrate how Clifford conjugation preserves the GHZ-class structure, and derive analytic expressions for exponential fidelity decay under layered Pauli noise. Numerical simulations and experimental data validate the scalability and robustness of the protocol, showing that it reliably characterizes device performance with minimal classical overhead. 

The resulting benchmark provides an efficient alternative for large-scale quantum devices operating beyond the reach of classical verification, bridging the gap between entanglement-based state characterization and scalable performance assessment.

In this study, adiabatically prepared Schrödinger’s cat states by starting in an eigenstate for noninteracting spins in a magnetic field in the x direction, and then converting the Hamiltonian to an Ising-model Hamiltonian with nearest-neighbor coupling of the z components of the spins.

We have explored both the forward and backward digitized evolution using Qiskit, with Trotterization of the time-evolution operator. Simulations were done on both a noiseless simulator and a fake backend, which has decoherence based on calibration data of IBMQ’s Manila.

Differences in the Shannon entropy during forward and backward evolution can be used to quantify the level of adiabaticity of the evolution, since truly adiabatic evolution should proceed through identical states, in either direction.

Links to presentations/posters:

MQC 2023 Poster

Schrödinger's cat states are maximally entangled n-qubit quantum states, which are a generalization of  the 3 spin 1/2 particle GHZ state. I am interested in the Shannon and von Neumann entropy, of the qubits in these coupled states.  By entangling qubits into large "cat" states.

We have seen that as the number of entangled qubits grows, there is a corresponding linear growth in Shannon entropy of the measurements.  I use IBM's publicly accessible quantum computers and Qiskit to create the entangled states. It is seen that the magnitude of the slope corresponds to the quality of the measured states. It is hoped that this finding can lead to a physically motivated classification of quality entanglement and provide a benchmark complementary to Quantum Volume .

This work has been published in PCCP: https://doi.org/10.1039/D1CP05255A

Links to presentations/posters:

ACS Fall 2023 Poster 

NMP Presentation