arXiv subjects

Shaul Mukamel

Publications and source records attributed to Shaul Mukamel.

At least 19 recordsLinked to original sources

arXiv2026

Photon entanglement-enhanced multidimensional spectroscopy of exciton correlations in photosynthetic aggregates

Nonlinear spectroscopic techniques using entangled photon pairs can provide an opportunity to exploit non-classical correlations encoded in two-photon wavefunctions to manipulate two-exciton wavefunctions. We propose an entangled photon pair-enhanced multidimensional spectroscopic technique that is sensitive to exciton-exciton interactions and correlations at the femtosecond timescale. Simulations for a dissipative system, namely, the photosynthetic aggregate reveal the superior ability of entangled photon pairs, compared to both transform-limited and frequency-chirped laser pulses, to manipulate excited-state absorption pathways. The corresponding spectral features in the two-dimensional spectrogram are interpreted in terms of one- and two-exciton resonances. The signal scales linearly with the incoming intensity of the photon sources. We show that classifying these resonances using entangled photon source in the perturbative limit allow for probing exciton correlations at the natural energy scale. These insights can be used to explore multi-exciton dynamics in molecular systems using multiphoton entanglement.

quant-ph↗

arXiv2026

Entangled photon pair excitation and time-frequency-filtered multidimensional photon correlation spectroscopy as a probe for dissipative exciton kinetics

In quantum aggregates, delocalized exciton states across energy manifolds interact with phonon modes, making state-resolved spectroscopic monitoring of dynamics challenging. We propose a scheme that combines photon-entanglement-enhanced narrowband excitation of two-exciton states with time-frequency-filtered two-photon coincidence counting, which allows high-resolution probing of dissipative two-exciton dynamics spread across multiple spectral and temporal windows. We demonstrate that entangled photon pairs can be used to prepare narrowband two-exciton population distributions, circumventing transport in the mediating one-exciton manifold, and the redistributed two-exciton population can be monitored using time-frequency-filtered two-photon coincidence counting. Numerical simulations for a light-harvesting aggregate highlight the ability of this protocol to suppress or amplify specific pathways under a realistic scenario. Combining entangled photonic sources with multidimensional photon correlation techniques enable promising applications in spectroscopy and sensing.

quant-ph↗

arXiv2025

Tracing long-lived atomic coherences generated via molecular conical intersections

Accessing coherences is key to fully understand and control ultrafast dynamics of complex quantum systems like molecules. Most photochemical processes are mediated by conical intersections (CIs), which generate coherences between electronic states in molecules. We show with accurate calculations performed on gas-phase methyl iodide that CI-induced electronic coherences of spin-orbit-split states persist in atomic iodine after dissociation. Our simulation predicts a maximum magnitude of vibronic coherence in the molecular regime of 0.75% of the initially photoexcited state population. Upon dissociation, one third of this coherence magnitude is transferred to a long-lived atomic coherence where vibrational decoherence can no longer occur. To trace these dynamics, we propose a table-top experimental approach--heterodyned attosecond four-wave-mixing spectroscopy (Hd-FWM). This technique can temporally resolve small electronic coherence magnitudes and reconstruct the full complex coherence function via phase cycling. Hence, Hd-FWM leads the way to a complete understanding and optimal control of spin-orbit-coupled electronic states in photochemistry.

physics.chem-ph↗

arXiv2025

Pump-intensity-scaling of Two-Photon-Absorption and Photon Statistics of Entangled-Photon Fields

We use a non-perturbative theoretical approach to the parametric down-conversion (PDC) process, which generates entangled-photon field for an arbitrarily strong pump-pulse. This approach can be used to evaluate multi-point field correlation functions to compute nonlinear spectroscopic signals induced by a strong pump. The entangled-photon statistics is studied using Glauber's $g^{(2)}$ function, which helps understand the significance of the photon entanglement-time and the pump-pulse intensity on spectroscopic signals. Under the non-perturbative treatment of the entangled field, the two-photon absorption (TPA) signal shows linear to strongly non-linear growth with the pump intensity, rather than linear to quadratic scaling reported previously. An increase in the range of pump intensity for the linear scaling is observed as the pump band-width is increased. We propose an experimental scheme that can select contributions to the TPA signal that arise solely from interactions with the entangled photons, and filter out unentangled photon contributions, which are dominant at higher pump intensities, paving a way to explore the entanglement effects at higher intensities.

physics.chem-ph↗

arXiv2024

Two-dimensional spectroscopy of open quantum systems

Two-dimensional spectroscopy is discussed for open quantum systems with multiple simultaneously measurable fluxes. In particular, we discuss a junction where optical measurements of photon flux are complemented with simultaneous transport measurements of electron currents. Theory of two-dimensional spectroscopy in both fluxes is developed employing non-self-consistent nonequilibrium Green's function formulation. Theoretical derivations are illustrated with numerical simulations within generic junction model.

cond-mat.mes-hall↗

arXiv2024

Nonlinear optical spectroscopy of open quantum systems

Development of experimental techniques at nanoscale resulted in ability to perform spectroscopic measurements on single-molecule current carrying junctions. These experiments are natural meeting point for research fields of optical spectroscopy and molecular electronics. We present a pedagogical comparison between perturbation theory expansion of standard nonlinear optical spectroscopy and (non-self-consistent) perturbative diagrammatic formulation of the nonequilibrium Green's functions method (NEGF is widely used in molecular electronics) indicating their similarities and differences. Comparing the two approaches we argue that optical spectroscopy of open quantum systems has to be analyzed within the more general Green's function formulation.

cond-mat.mes-hall↗

arXiv2024

NSF-UKRI Bilateral Workshop: Quantum Information Science in Chemistry

This document summarizes the context and main outcomes of the discussions that took place during the NSF-UKRI bilateral workshop on Quantum Information Science in Chemistry, held on 12-13 February 2024, in Alexandria, Virginia (US). The workshop was jointly funded by the National Science Foundation (NSF) and UK Research and Innovation (UKRI) through the Engineering and Physical Sciences Research Council (EPSRC). It brought together scientific delegations from the United States of America (US) and the United Kingdom (UK).

quant-ph↗

arXiv2024

Stimulated X-ray Raman scattering for selective preparation of dark states bypassing optical selection rules

We present an X-ray based stimulated Raman approach to control the preparation of optically dark electronic states in generic molecular systems. Leveraging on the unique properties of core-level excited states, we demonstrate that optically forbidden transitions between singlet states, or between singlet and triplet states are made accessible. Two molecular systems are studied as a test-bed of the proposed approach, and its experimental feasibility is eventually discussed.

physics.chem-ph↗

arXiv2024

Temperature dependence of Coherent versus spontaneous Raman Scattering

Due to their sub picosecond temporal resolution, coherent Raman spectroscopies have been proposed as a viable extension of Spontaneous Raman (SR) thermometry, to determine dynamics of mode specific vibrational energy content during out of equilibrium molecular processes. Here we show that the presence of multiple laser fields stimulating the vibrational coherences introduces additional quantum pathways, resulting in destructive interference. This ultimately reduces the thermal sensitivity of single spectral lines, nullifying it for harmonic vibrations and temperature independent polarizability. We demonstrate how harnessing anharmonic signatures such as vibrational hot bands enables coherent Raman thermometry.

physics.optics↗

arXiv2023

Opportunities for Gas-Phase Science at Short-Wavelength Free-Electron Lasers with Undulator-Based Polarization Control

Free-electron lasers (FELs) are the world's most brilliant light sources with rapidly evolving technological capabilities in terms of ultrabright and ultrashort pulses over a large range of accessible photon energies. Their revolutionary and innovative developments have opened new fields of science regarding nonlinear light-matter interaction, the investigation of ultrafast processes from specific observer sites, and approaches to imaging matter with atomic resolution. A core aspect of FEL science is the study of isolated and prototypical systems in the gas phase with the possibility of addressing well-defined electronic transitions or particular atomic sites in molecules. Notably for polarization-controlled short-wavelength FELs, the gas phase offers new avenues for investigations of nonlinear and ultrafast phenomena in spin orientated systems, for decoding the function of the chiral building blocks of life as well as steering reactions and particle emission dynamics in otherwise inaccessible ways. This roadmap comprises descriptions of technological capabilities of facilities worldwide, innovative diagnostics and instrumentation, as well as recent scientific highlights, novel methodology and mathematical modeling. The experimental and theoretical landscape of using polarization controllable FELs for dichroic light-matter interaction in the gas phase will be discussed and comprehensively outlined to stimulate and strengthen global collaborative efforts of all disciplines.

physics.atom-ph↗

arXiv2023

Qubit entanglement generated by classical light driving an optical cavity

We study the generation of entanglement between two qubits which communicate through a single cavity mode of quantum light but have no direct interaction. We show that such entanglement can be generated simply by exchanging quanta with a third party, which is in our case the cavity mode. Exchanging only a single quantum creates maximal entanglement. A single quantum can be provided by an external quantum light source. However, we use a classical light source to pump quanta which are used for the exchange, and investigate the degree of two-qubit entanglement. We first identify a characteristic timescale of the interaction between the cavity mode and each qubit. We investigate two regimes of the driving pulse length, one is short and the other is long compared to the characteristic timescale of the interaction. In the first regime, it is known that the pulse can pump the system by generating a displacement of the cavity mode. We show that, by using a specific pulse shape, one can make the displacement to essentially vanish after the pulse finishes interaction with the cavity mode. In this case, a rotation of the qubits can be invoked. In addition, higher-order effects of the pulse including a non-local operation on the joint system of the cavity mode and the qubits are found, and we present a formalism to compute each term up to a given order. An explicit condition on the pulse shape for each term to be nonzero or suppressed is derived to enable an experimental design for verifying the entanglement generation using a classical light source. In the opposite regime where the driving is sufficiently long, we utilize a squeezed state which may be obtained adiabatically. We study how the squeezing and the accompanied rotation of qubits affect the generated two-qubit entanglement.

quant-ph↗

arXiv2023

Exceptional points treatment of cavity spectroscopies

The infrared response of a system of two vibrational modes in a cavity is calculated by an effective non-Hermitian Hamiltonian derived by employing the nonequilibrium Green's functions (NEGF) formalism. Degeneracies of the Hamiltonian (exceptional points, EP) widely employed in theoretical analysis of optical cavity spectroscopies are used in an approximate treatment and compared with the full NEGF. Qualitative limitations of the EP treatment are explained by examining the approximations employed in the calculation.

cond-mat.mes-hall↗

arXiv2022

Magnet-Free Time-Resolved Magnetic Circular Dichroism with Pulsed Vector Beams

Magnetic circular dichroism (MCD) is a widely used spectroscopic technique which reveals valuable information about molecular geometry and electronic structure. However, the weak signal and the necessary strong magnets impose major limitations on its application. We propose a novel protocol to overcome these limitations by using pulsed vector beams (VBs), which consist of nanosecond gigahertz pump and femtosecond UV-Vis probe pulses. By virtue of the strong longitudinal electromagnetic fields, the MCD signal detected by using the pulsed VBs is greatly enhanced compared to conventional MCD performed with plane waves. Furthermore, varying the pump-probe time delay allows to monitor the ultrafast variation of molecular properties.

physics.chem-ph↗

arXiv2022

Molecular chirality and its monitoring by ultrafast X-ray pulses

Major advances in X-ray sources including the development of circularly polarized and orbital angular momentum pulses make it possible to probe matter chirality at unprecedented energy regimes and with Angström and femtosecond spatiotemporal resolutions. We survey the theory of stationary and time-resolved nonlinear chiral measurements that can be carried out in the X-ray regime using tabletop X-ray sources or large scale (XFEL, synchrotron) facilities. A variety of possible signals and their information content are surveyed.

physics.chem-ph↗

arXiv2022

Unique Signatures of Topological Phases in Two-Dimensional THz Spectroscopy

We develop a microscopic theory for the two-dimensional spectroscopy of one-dimensional topological superconductors. We consider a ring geometry as a realization of the Kitaev chain with periodic boundary conditions. We show numerically and analytically that the cross-peak structure of the 2D spectra carries unique signatures of the topological phases of the chain. Our work reveals how 2D spectroscopy can identify topological phases in bulk properties, bypassing energy-specific differences caused by topologically protected or trivial boundary modes that are otherwise hard to distinguish.

cond-mat.mes-hall↗

arXiv2022

Nonlinear quantum interferometric spectroscopy with entangled photon pairs

We develop closed expressions for a time-resolved photon counting signal induced by an entangled photon pair in an interferometric spectroscopy setup. Superoperator expressions in Liouville-space are derived that can account for relaxation and dephasing induced by coupling to a bath. Interferometric setups mix matter and light variables non-trivially, which complicates their interpretation. We provide an intuitive modular framework for this setup that simplifies its description. Based on separation between the detection stage and the light-matter interaction processes. We show that the pair entanglement time and the interferometric time-variables control the observed physics time-scale. Only a few processes contribute in the limiting case of small entanglement time with respect to the sample response, and specific contributions can be singled out.

quant-ph↗

arXiv2021

Excited-state energy surfaces in molecules revealed by impulsive stimulated Raman excitation profiles

Photophysical and photochemical processes are ruled by the interplay between transient vibrational and electronic degrees of freedom, which are ultimately determined by the multidimensional potential energy surfaces (PESs). Differences between ground and excited PESs are encoded in the relative intensities of resonant Raman bands, but they are experimentally challenging to access requiring measurements at multiple wavelengths under identical conditions. Here we perform a two-color impulsive vibrational scattering experiment to launch nuclear wavepacket motions by an impulsive pump and record their coupling with a targeted excited-state potential by resonant Raman processes with a delayed probe, generating in a single-measurement background-free vibrational spectra across the entire sample absorption. Building on the interference between the multiple pathways resonant with the excited-state manifold that generate the Raman signal, we show how to experimentally tune their relative phase by varying the probe chirp, decoding nuclear displacements along different normal modes and revealing the multidimensional PESs. Our results are validated against time-dependent density functional theory.

physics.chem-ph↗

arXiv2021

Wavepacket control and simulation protocol for entangled two-photon-absorption of molecules

Quantum light spectroscopy, providing novel molecular information non-accessible by classical light, necessitates new computational tools when applied for complex molecular systems. We introduce two computational protocols for the molecular nuclear wave packet dynamics interacting with an entangled photon pair to produce the entangled two-photon absorption signal. The first involves summing over transition pathways in a temporal grid defined by two light-matter interaction times accompanied by the field correlation functions of quantum light. The signal is obtained by averaging over the two-time distribution characteristic of the entangled photon state. The other protocol involves a Schmidt decomposition of the entangled light and requires summing over the Schmidt modes. We demonstrate how photon entanglement can be used to control and manipulate the two-photon excited nuclear wave packets in a displaced harmonic oscillator model.

physics.chem-ph↗