arXiv subjects

J. E. Sipe

Publications and source records attributed to J. E. Sipe.

At least 19 recordsLinked to original sources

arXiv2026

Coherent control of photon pairs via quantum interference between second- and third-order quantum nonlinear processes

Genuine quantum interference between independent nonlinear processes of different order provides a route to coherent control that cannot be reduced to a classical field interference. Here we present an all-optical analogue of coherent carrier injection by exploiting interference between second- and third-order quantum nonlinear processes in an integrated photonic platform. Photon pairs generated via spontaneous parametric down-conversion and spontaneous four-wave mixing coherently contribute to the same final two-photon state, resulting in a phase-dependent modulation of both the generation rate and the spectral structure of the emitted biphoton state. We illustrate the features of such interference and how it can be used to shape biphoton wavefunctions and their quantum correlations. These results identify interference between nonlinear processes of different order as a distinct form of coherent quantum control within quantum nonlinear optics.

physics.optics↗

arXiv2026

Multi-photon schemes for mid-infrared detection : Comparative study of bulk GaAs and Ge$_{1-x}$Sn$_x$

We calculate the theoretical non-degenerate two photon absorption and three color injected current response tensors for bulk GaAs and Ge$_{1-x}$Sn$_x$ for a range of alloy compositions. In particular, by including a ''pump'' beam we compare two ''schemes'' that are sensitive to mid-infrared photons. In ''scheme I'' we consider GaAs and a pump photon with energy greater than half the band gap, and in ''scheme II'' we consider Ge$_{1-x}$Sn$_x$ with a pump photon with energy less than half the band gap. We find that for certain pump and alloy concentrations Ge$_{1-x}$Sn$_x$ has a substantially larger nonlinear response and three-color injected current than GaAs in the mid-infrared frequency window where both materials can absorb photons via non-degenerate two-photon absorption.

cond-mat.mtrl-sci↗

arXiv2026

Joint spectral characterization of SPDC photon pairs near 2 $μ$m in (Al)GaAs-on-insulator waveguides

Integrated photon-pair sources are a core component of chip-based quantum computing, communication, and metrology. Although such sources have been demonstrated at conventional telecom wavelengths, the 2 $μ$m band remains comparatively less explored, despite offering advantages for free-space quantum communication, low-loss transmission in emerging fiber networks, and integration with silicon photonic platforms. In this paper, we demonstrate spontaneous parametric down-conversion (SPDC) in straight GaAs- and AlGaAs-on-insulator waveguides. This platform offers strong second-order nonlinearity and geometry-tunable dispersion, which are advantageous for efficient on-chip pair generation. Measurements of the joint spectral intensity and heralded second-order correlation function show broadband emission around 2 $μ$m with strong spectral anti-correlations. To our knowledge, this is the first direct joint-spectral characterization of an integrated SPDC source in this wavelength regime.

physics.optics↗

arXiv2026

A new perspective on the anomalous Hall effect

We revisit the anomalous Hall effect in magnetic conductors, and its generalization to finite frequencies, using a formalism based on microscopic notions of polarization, magnetization, and free charges and currents. The electronic degrees of freedom are treated within second-quantized field theory, where the Hamiltonian features a static and cell-periodic magnetic field that encodes the magnetic order in the crystal and breaks time-reversal symmetry. We study the dynamics of bound and free charge carriers at the microscopic level as they respond to a spatially uniform electric field at finite frequency. The conductivity tensor describing the long-wavelength response is a sum of three terms, including a Kubo term associated with the polarization response, along with the metallic Drude term and the anomalous Hall conductivity that are associated with the longitudinal and transverse parts of the free current response, respectively. We also present numerical calculations of these contributions for the ferromagnetic body-centered cubic phase of iron.

cond-mat.mes-hall↗

arXiv2026

Squeezing Enhancement Through Resonant Interference in Multi-ring Resonators

We develop a non-perturbative description of squeezed light generation in an arbitrary lossy structure consisting of multiple coupled microring resonators. This is applied to two ring photonic molecules where the interference of the fields in the coupled rings leads to a modification in the resonance spectrum near a shared resonance. Considering a dual-pump degenerate squeezing scheme under a five resonance approximation, we investigate two methods to suppress parasitic four-wave mixing contributions and compensate for group velocity dispersion within a primary resonator through hybridization effects with a second auxiliary resonator. In the former case, this comes from an effective splitting of the unwanted resonances supporting parasitic four-wave mixing interactions that add thermal noise to the desired degenerate squeezed state. For sufficiently strong coupling between the resonators, we demonstrate near complete suppression of such parasitic processes, resulting in near unit fidelities with the corresponding output state that would arise were the parasitic interactions neglected. In the latter case, the hybridization effectively shifts a pump resonance, realigning the desired dual-pump four-wave mixing process and leading to a significant enhancement of the signal generation and output squeezing.

quant-ph↗

arXiv2026

Linear response of the Chern insulator MnBi$_2$Te$_4$: A Wannier function approach

Recent work demonstrated that in the long wavelength limit the linear response of a Chern insulator to finite-frequency electric fields is the sum of two terms: A general frequency-dependent Kubo contribution that is present irrespective of band topology, and a topological Hall term that vanishes for topologically trivial insulators. Motivated by recent experiments and theoretical predictions, we use these expressions to calculate the optical conductivity and susceptibility of intrinsically magnetic MnBi$_2$Te$_4$ thin films with one, four, five, and eleven septuple layers by combining density functional theory with "single-shot" Wannier functions. To characterize the underlying topology of these systems, we compute the two-dimensional Chern number of these films using recently derived global expressions formulated in terms of Bloch energies and velocity matrix elements; the use of these expressions allows us to circumvent numerical issues at band crossings. Films with eleven septuple layers are of particular interest. We find that they have the same Chern number as five septuple layer films, in contrast to the reported "higher Chern-number phase" of these systems in other studies; we discuss a few possible reasons for the discrepancy. We also identify spin-orbit coupling-driven band inversions as a possible indicator of these topological phases.

cond-mat.mes-hall↗

arXiv2026

Theory of the two-photon Franz-Keldysh effect and electric-field-induced bichromatic coherent control

The effect of a constant electric field on two-photon absorption in a semiconductor is calculated using an independent-particle theory. The theoretical framework is an extension of a theory of the one-photon Franz-Keldysh effect [Wahlstrand and Sipe, Phys. Rev. B 82, 075206 (2010)]. The theory includes the effect of the constant field, including field-induced coupling between closely spaced bands, in the electronic wavefunctions and calculates optical absorption perturbatively. Numerical calculations are performed using a 14-band $\mathbf{k} \cdot\mathbf{p}$ band structure model for GaAs. For all nonzero tensor elements, field-enabled two-photon absorption (TPA) below the band gap and Franz-Keldysh oscillations in the TPA spectrum are predicted, with a generally larger effect in tensor elements with more components parallel to the constant electric field direction. Some tensor elements that are zero in the absence of a field become nonzero in the presence of the constant electric field and depend on its sign. Notably, these elements are linear in the electric field to lowest order and may be substantial away from band structure critical points at room temperature and/or with a non-uniform field. Electric-field-induced changes in the carrier injection rate due to interference between one- and two-photon absorption are also calculated. The electric field enables this bichromatic coherent control process for polarization configurations where it is normally forbidden, and also modifies the spectrum of the process for configurations where it is allowed by crystal symmetry.

physics.optics↗

arXiv2026

Photon triplets from integrated microrings: A path towards deterministic non-Gaussianity on a chip

We propose cascaded spontaneous four-wave mixing (SFWM) in microring resonators as a scalable and efficient approach for directly generating non-Gaussian states of light. Focusing on the well-understood "low-gain" regime, we demonstrate that triplet generation through cascaded SFWM can be achieved with high efficiency and favorable spectral characteristics using realistic microring sources in AlGaAs. The ability to achieve the generation of light in a single set of supermodes -- and the predicted accessibility of the "high-gain" regime at realistic pump powers -- makes this source a promising candidate as a direct and deterministic source of non-Gaussian light for photonic quantum information processing.

quant-ph↗

arXiv2026

Chern insulators in two and three dimensions: A global perspective

We introduce a second-quantized field theory for Chern insulators in which the Hamiltonian features a static vector potential that has the periodicity of the crystal's lattice and spontaneously breaks time-reversal symmetry in the system's ground state. Such a vector potential generates a magnetic field at the microscopic level that may be thought of as arising from local moments associated with one or more magnetic ions in each unit cell. Considering spinor electrons, we study the Chern invariants characterizing the topology of the occupied valence bands of Chern insulators in both two and three dimensions - the Chern number and the Chern vector, respectively - and we derive novel expressions for these topological invariants that are globally defined across the Brillouin zone and involve the full band structure of the system. We also study the long-wavelength response of a Chern insulator to electromagnetic fields at finite frequency, generalizing the quantum anomalous Hall effect in the static limit to the optical regime.

cond-mat.mes-hall↗

arXiv2025

Photodetection of Squeezed Light: a Whittaker-Shannon Analysis

The Whittaker-Shannon decomposition provides a temporally localized description of squeezed light, making it applicable in the CW limit and leading to a definition of squeezing strength based on the number of photon pairs at a time. We show examples of its usefulness by calculating quadrature variance in a homodyne detection scheme, coincidence detection probabilities in the continuous-wave limit, and analyzing the Hong-Ou-Mandel effect for strongly squeezed light. Quadrature uncertainty falls farther below the shot noise limit when squeezing is strong, but effects due to correlations between photon pairs are most significant with weak squeezing. Our analysis extends previous results to more general scenarios, and we leverage the Whittaker-Shannon formalism to interpret them based on the temporal properties of photon pairs.

quant-ph↗

arXiv2025

Non-Gaussian states via pump-depleted SPDC

We develop a model for non-Gaussian state generation via spontaneous parametric down-conversion (SPDC) in InGaP microring resonators. The nonlinear Hamiltonian is written in terms of the asymptotic fields for the system, which includes a phantom channel to handle scattering loss. The full ket for the system is written as a Gaussian unitary acting on a residual non-Gaussian ket, which is vacuum initially and evolves according to a non-Gaussian Hamiltonian. We show that for realistic parameters we can access the pump depletion regime, where the Wigner function for the residual non-Gaussian ket has negativity. But we find that the non-Gaussian features for the full ket could be unobservable due to the large amount of squeezing required to lead to pump depletion. We show that a potential solution in the low-loss regime is to implement an inverse Gaussian unitary on the accessible modes to remove most of the squeezing and reveal the non-Gaussian features. This work provides a foundation for modeling pump-depleted SPDC in integrated lossy microring resonators, opening a path toward a scalable on-chip non-Gaussian source.

quant-ph↗

arXiv2025

High gain squeezing in lossy resonators: an asymptotic field approach

We present a method for describing nonlinear electromagnetic interactions in integrated photonic devices utilizing an asymptotic-in/out field formalism. Our method expands upon previous continuous wave asymptotic treatments by describing the evolution non-perturbatively for an arbitrary pulsed input. This is presented in the context of a squeezing interaction within an integrated microring resonator side coupled to an input/output waveguide, but is readily generalizable to other integrated structures, while including a variety of (non-squeezing) third-order interactions. An example of a single-pump, non-degenerate squeezing interaction is studied, which is shown to match well with standard coupled-mode treatments for high-finesse resonators, as well as previous perturbative treatments dealing with the generation of pairs with low probability.

quant-ph↗

arXiv2025

Frequency Dependent Magnetic Susceptibility and the $q^2$ effective conductivity tensor

We apply a microscopic formalism for the calculation of material response properties to the problem of the generalization of a first-principles, i.e based on the energy spectrum and geometric properties of the Bloch functions, derivation of the AC magnetic susceptibility. We find that the AC susceptibility forms only a part of the $q^2$ -- where $q$ is the wavevector of the applied field -- effective conductivity tensor, and many additional response tensors characterizing both electric and magnetic multipole moments response to electromagnetic fields and their derivatives must be included to create the full gauge-invariant response. As was seen with the DC magnetic susceptibility and optical activity (characterized by the linear in $q$ contribution to the conductivity) one must be careful with the diagonal elements of the Berry connection. To our knowledge this is the only derivation of such a result general for crystalline insulators, with both `atomic like' contributions and `itinerant contributions' due to overlap of atomic orbitals and non-flat bands. Additionally, quantities familiar from quantum geometry like the Berry connection, curvature, and quantum metric appear extensively.

cond-mat.mes-hall↗

arXiv2025

Photon pair generation via down-conversion in III-V semiconductor microrings: modal dispersion and quasi-phase matching

We explore how III-V semiconductor microring resonators can efficiently generate photon pairs and squeezed vacuum states via spontaneous parametric down-conversion by utilizing their built-in quasi phase matching and modal dispersion. We present an analytic expression for the biphoton wave function of photon pairs generated by weak pump pulses, and characterize the squeezed states that result under stronger pumping conditions. Our model includes loss, and captures the statistics of the scattered photons. A detailed sample calculation shows that for low pump powers conversion efficiencies of 10$^{-5}$, corresponding to a rate of $39$ MHz for a pump power of 1 $μ$W, are attainable for rudimentary structures such as a simple microring coupled to a waveguide, in both the continuous wave and pulsed excitation regimes. Our results suggest that high levels of squeezing and pump depletion are attainable, possibly leading to the deterministic generation of non-Gaussian states.

quant-ph↗

arXiv2025

Linear response of a Chern insulator to finite-frequency electric fields

We derive the macroscopic charge and current densities of a Chern insulator initially occupying its electronic ground state as it responds to a finite-frequency electric field; we use a previously developed formalism based on microscopic polarization and magnetization fields in extended media. In a topologically trivial insulator, our result reduces to the familiar expression for the induced current density in linear response obtained from a Kubo analysis. But for a Chern insulator we find an extra "topological" term involving the (first) Chern number associated with the occupied bands, encoding the quantum anomalous Hall effect in the presence of a frequency-dependent electric field. While an analogous term has been introduced in the "modern theories of polarization and magnetization" for the linear response of finite-sized systems to static electric fields, our expression is valid for bulk Chern insulators in the presence of both static and finite-frequency electric fields, being derived analytically from a microscopic treatment of the electronic degrees of freedom, and can be generalized in a straightforward way to describe the response of a Chern insulator to electromagnetic fields that are not only frequency-dependent but also spatially inhomogeneous.

cond-mat.mes-hall↗

arXiv2024

Programmable integrated source of polarization and frequency-bin hyperentangled photon pairs

We present a system of four ring resonators capable of generating programmable polarization and frequency-bin entangled photon pairs on an integrated photonic device. Each ring is pumped with a continuous wave, generating photon pairs with the same polarization in two pairs of frequency bins via spontaneous fourwave mixing. We show that the density operator of the generated state represents a hyperentangled state in the polarization and frequency bin degrees of freedom. We also calculate the generation rate of the state.

quant-ph↗

arXiv2024

Photonic multipartite entanglement in discrete variables without arbitrary unitaries

We present an approach for designing sources of postselected multipartite states based on photon-pair sources. Our approach can be applied to arbitrary target states in different encoding schemes and physical platforms. It also allows one to limit the types of components to be used in the device, such that lossy or difficult-to-implement optical elements can be avoided. As an example, we apply this strategy to design a passive integrated source of frequency-bin-encoded high-dimensional GHZ states with a 10 kHz on-chip generation rate for picojoule pump pulses.

quant-ph↗

arXiv2023

Quantum-Referenced Spontaneous Emission Tomography

We present a method of tomography that measures the joint spectral phase (JSP) of spontaneously emitted photon pairs originating from a largely uncharacterized ``target" source. We use quantum interference between our target source and a reference source to extract the JSP with four spectrally resolved measurements, in a process that we call quantum-referenced spontaneous emission tomography (Q-SpET). We have demonstrated this method on a photonic integrated circuit for a target micro-ring resonator photon-pair source. Our results show that spontaneously emitted photon pairs from a micro-ring resonator are distinctively different from that of stimulated emission, and thus cannot in general be fully characterized using classical stimulated emission tomography without detailed knowledge of the source.

quant-ph↗