arXiv subjects

Tim Thomay

Publications and source records attributed to Tim Thomay.

12 recordsLinked to original sources

arXiv2026

Information capacity of quantum statistics: Fock-state tests of a discrete binary-sequence model on cloud photonic quantum processors

Our central premise is that quantum mechanics may be the statistical limit of a more fundamental discrete theory: any such theory equips a physical system with a finite information capacity, and its departure from quantum statistics is controlled by how much of that capacity the system uses. We show that commercial cloud photonic quantum processors have reached the precision required to bound this capacity from below, using the binary-sequence model of Powers et al. as the concrete test theory: outcome probabilities arise from counting discrete sequences of length $n$, quantum mechanics is recovered as $n \to \infty$, and $n$ measures the information capacity of the register behind a prepared state. Photon Fock states $|1\rangle$, $|1,1\rangle$, heralded $|2\rangle$, and cascaded beam-splitter pairs are measured on programmable interferometers with dominant systematics determined in situ. The model's composition-consistent parametrization, singled out by requiring that rotations compose, recovers quantum mechanics with deviations $1.24/n$; a random-effects likelihood analysis calibrated by parametric bootstrap excludes all $n \le 100$: the information capacity of the register carrying the two-photon state, if finite, exceeds $10^2$. Cascaded beam splitters test the composition law directly: the data are split-invariant, excluding naive count composition at $8\sigma$ and confirming the interference-sign rule. Model-independently, curve-averaged deviations from the quantum partition law larger than $2.3\times10^{-2}$ are excluded at 95% CL, and the originally published linear parametrization is excluded outright. Because the compilation offset is frozen per circuit it is calibratable, opening the $10^{-3}$ floor ($n \sim 10^3$) to current hardware: cloud photonic processors are quantitative instruments for quantum foundations, and information capacity an experimentally boundable quantity.

quant-ph↗

arXiv2026

One knob to tune them all: Phase-controlled photon statistics and linewidth in partially pumped atomic ensembles

We study a minimal model of collective light emission from an incoherently driven ensemble of atoms where incoherent drive is applied to only a subset of the atoms and show that both the linewidth and the photon statistics can be controlled within a single framework. In this setting, collective dissipation induces correlations between the pumped and unpumped parts of the system, leading to interference between their emission contributions. By introducing a relative phase between these contributions and tuning the pump rate, we demonstrate that the properties of the emitted light can be varied over a broad range. In particular, the linewidth can be made either independent of system size or scale extensively with it, while the photon statistics can be tuned from antibunched or quantum to bunched. We further show that the role of the relative phase in controlling the interference can alternatively be played by the coherent interaction. By tuning the interaction strength together with the pump rate, one can access the same regimes as in the dissipation-only model. In addition, coherent interactions stabilize regimes of coherent emission with narrow linewidth, reminiscent of superradiant lasing. Our results illustrate how interference in partially driven collective systems provides a flexible mechanism for tailoring both spectral and statistical properties of light.

quant-ph↗

arXiv2025

Spectrally Resolved Higher Order Photon Statistics of Spontaneous Parametric Down Conversion

The photon statistics of Spontaneous Parametric Down Conversion (SPDC) exhibit dependencies on wavelength, pump power, and coincidence time. Notably, the average photon numbers were found to asymmetrically increase with increasing pump power around the degenerate wavelength of emission. By the coupling of the detection scheme to a spectrometer, studying different bandwidths within the emission revealed that shorter wavelengths increased nonlinearly with pump power, while longer wavelengths showed more linear behavior, indicating a wavelength dependent efficiency in the generation of the SPDC. We employ the use of a four detector Hanbury Brown and Twiss Interferometer to study the photon statistics of the signal beam, where the idler serves as the herald. The measured statistics were found to be best described by a Negative Binomial Distribution, which is a characteristic of thermal light sources. The detection and characterization of complex light sources has wide ranging applications in the fields of quantum metrology, quantum communications, and quantum computing, more specifically, a system that is sensitive to wavelength and photon number distribution.

quant-ph↗

arXiv2025

Utilizing Quantum Fingerprints in Plant Cells to Evaluate Plant productivity

Overcoming the strong chlorophyll background poses a significant challenge for measuring and optimizing plant growth. This research investigates the novel application of specialized quantum light emitters introduced into intact leaves of tobacco (Nicotiana tabacum), a well-characterized model plant system for studies of plant health and productivity. Leaves were harvested from plants cultivated under two distinct conditions: low light (LL), representing unhealthy leaves with reduced photosynthesis. and high light (HL), representing healthy leaves with highly active photosynthesis. Higher-order correlation data were collected and analyzed using machine learning (ML) techniques, specifically a Convolutional Neural Network (CNN), to classify the photon emitter states. This CNN efficiently identified unique patterns and created distinct fingerprints for Nicotiana leaves grown under LL and HL, demonstrating significantly different quantum profiles between the two conditions. These quantum fingerprints serve as a foundation for a novel unified analysis of plant growth parameters associated with different photosynthetic states. By employing CNN, the emitter profiles were able to reproducibly classify the leaves as healthy or unhealthy. This model achieved high probability values for each classification, confirming its accuracy and reliability. The findings of this study pave the way for broader applications, including the application of advanced quantum and machine learning technologies in plant health monitoring systems.

physics.bio-ph↗

arXiv2025

Photon statistics of time dependent electronic excitation of spin injected quantum dots

The time dynamics of spin-injected, electrically contacted quantum dots were investigated with a focus on the time evolution of photon statistics. Photon statistics can provide insights into whether the device functions as an effective single-photon emitter or exhibits higher-order emissions. Through these investigations, we found that the shape of the electrical excitation pulse has a direct impact on photon statistics. Specifically, the rising edge of the pulse corresponds to a significantly higher number of higher-order photon states, which decay much faster than single photons associated with the falling edge of the electrical pulse. This relationship implies that the pulse shape can be tailored to optimize the device as either a better single-photon source or a generator of higher-order photon states, with potential applications in creating deterministic higher-order photon Fock states. The ability to easily modify the pulse shape is a unique feature of electrically excited quantum dots.

quant-ph↗

arXiv2024

Electronic readout of optically excited surface plasmons

Leveraging thermal losses as a useful consequence of surface plasmons in metal nanostructures has gained traction in recent years. This thermalization of hot electrons also induces a resistance change to an applied bias current, which we use to realize an all electronic readout of surface plasmons. The interplay of the plasmonic k-vector dependence and the applied bias current allows us to distinguish between linear polarizations of an incident laser beam for polarimetry and polarization imaging uses. This illustrates the potential applications this technique offers as a fully CMOS compatible plasmonic sensor. Moreover, we demonstrate an electronic signal that depends on the delay between two laser pulses on ultrafast timescales, providing insight into the highly non-equilibrium dynamics of the hot electron distribution inside the metal. Using an electronic approach to surface plasmons broadens access and simplifies existing applications, while simultaneously opening the door to new pathways for developing integrated sensors for processes on ultrafast timescales.

physics.optics↗

arXiv2024

Optimized higher-order photon state classification by machine learning

The classification of higher-order photon emission becomes important with more methods being developed for deterministic multiphoton generation. The widely-used second-order correlation g(2) is not sufficient to determine the quantum purity of higher photon Fock states. Traditional characterization methods require a large amount of photon detection events which leads to increased measurement and computation time. Here, we demonstrate a Machine Learning model based on a 2D Convolutional Neural Network (CNN) for rapid classification of multiphoton Fock states up to |3> with an overall accuracy of 94%. By fitting the g(3) correlation with simulated photon detection events, the model exhibits efficient performance particularly with sparse correlation data, with 800 co-detection events to achieve an accuracy of 90%. Using the proposed experimental setup, this CNN classifier opens up the possibility for quasi real-time classification of higher photon states, which holds broad applications in quantum technologies.

quant-ph↗

arXiv2023

A statistical model for quantum spin and photon number states

The most irreducible way to represent information is a sequence of two symbols. In this paper, we construct quantum states using this basic building block. Specifically, we show that the probabilities that arise in quantum theory can be reduced to counting more fundamental ontic states, which we interpret as event networks and model using sequences of 0's and 1's. A completely self contained formalism is developed for the purpose of organizing and counting these ontic states, which employs the finite cyclic group $\mathbb{Z}_2 = \{0, 1\}$, basic set theory, and combinatorics. This formalism is then used to calculate probability distributions associated with particles of arbitrary spin interacting with sequences of two rotated Stern-Gerlach detectors. A central ingredient of this construction is the rule which converts the abstract counts labelling an operation into the physical angle of rotation it represents. We show that this rule is not linear in the counts, but is instead fixed by the half-angle law $\tan(\theta_{ab}/2)=\tilde{B}_{map}/\tilde{A}_{map}$, which is the unique assignment consistent with the composition of successive rotations. These calculations are compared with the predictions of non-relativistic quantum mechanics and shown to agree exactly in the limit of large sequence length $n$, with finite $n$ corrections which vanish as $O(1/n)$ and with no free or fitted parameters. The residual deviation at finite $n$ does not lead to violations of relevant no-go theorems, such as Bell's inequalities, the Kochen-Specker theorem, or the PBR theorem. The proposed model is then extended to an optical system involving photon number states passing through a beam splitter. Leveraging recent advancements in high precision experiments on these systems, we then propose a means of testing the new model using a tabletop experiment.

quant-ph↗

arXiv2019

Fabrication of BaZrS3 chalcogenide perovskite thin films for optoelectronics

BaZrS3 is a prototypical chalcogenide perovskite, an emerging class of unconventional semiconductor. Recent results on powder samples reveal that it is a material with a direct band gap of 1.7-1.8 eV, a very strong light-matter interaction, and a high chemical stability. However, many of the fundamental properties are unknown, hindering the ability to apply BaZrS3 for optoelectronics. Here we report the fabrication of BaZrS3 thin films, by sulfurization of oxide films deposited by pulsed laser deposition. We show that these films are n-type with carrier densities in the range of 10^19-10^20 cm^-3. Depending on the processing temperature, the Hall mobility ranges from 2.1 to 13.7 cm^2/Vs. The absorption coefficient is > 10^5 cm-1 at photon energy > 1.97 eV. Temperature dependent conductivity measurements suggest shallow donor levels. These results assure that BaZrS3 is a promising candidate for optoelectronics such as photodetectors, photovoltaics, and light emitting diodes.

cond-mat.mtrl-sci↗

arXiv2017

Simultaneous, full characterization of a single-photon state using semiconductor quantum-dot light

As single-photon sources become more mature and are used more often in quantum information, communications and measurement applications, their characterization becomes more important. Single-photon-like light is often characterized by its brightness, and two quantum properties: the single-photon composition and the photon indistinguishability. While it is desirable to obtain these quantities from a single measurement, currently two or more measurements are required. Here, we simultaneously determine the brightness, the single photon purity, the indistinguishability, and the statistical distribution of Fock states to third order for a quantum light source. The measurement uses a pair of two-photon (n = 2) number-resolving detectors. n > 2 number-resolving detectors provide no additional advantage in the single-photon characterization. The new method extracts more information per experimental trial than a conventional measurement for all input states, and is particularly more e cient for statistical mixtures of photon states. Thus, using this n=2, number- resolving detector scheme will provide advantages in a variety of quantum optics measurements and systems.

quant-ph↗

arXiv2012

Dynamics of the non-classical light from a single solid-state quantum emitter

We measure the dynamics of a non-classical optical field using two-time second-order correlations in conjunction with pulsed excitation. The technique quantifies single-photon purity and coherence during the excitation-decay cycle of an emitter, illustrated here using a quantum dot. We observe that for certain pump wavelengths, photons detected early in the cycle have reduced single-photon purity and coherence compared to those detected later. A model indicates that the single-photon purity dynamics are due to exciton recapture after initial emission and within the same pulse cycle.

quant-ph↗

arXiv2012

Femtosecond nonlinear ultrasonics in gold probed with ultrashort surface plasmons

Fundamental interactions induced by lattice vibrations on ultrafast time scales become increasingly important for modern nanoscience and technology. Experimental access to the physical properties of acoustic phonons in the THz frequency range and over the entire Brillouin zone is crucial for understanding electric and thermal transport in solids and their compounds. Here, we report on the generation and nonlinear propagation of giant (1 percent) acoustic strain pulses in hybrid gold/cobalt bilayer structures probed with ultrafast surface plasmon interferometry. This new technique allows for unambiguous characterization of arbitrary ultrafast acoustic transients. The giant acoustic pulses experience substantial nonlinear reshaping already after a propagation distance of 100 nm in a crystalline gold layer. Excellent agreement with the Korteveg-de Vries model points to future quantitative nonlinear femtosecond THz-ultrasonics at the nano-scale in metals at room temperature.

physics.optics↗