Academic Career

• • EPISTEME99 | Feb 2023 - Present | Founder, PI 

Adapting AI algorithms to solve high-throughput I/O problems in quantum computing. Beyond the "initial pitch", the theoretical techniques in development focus on reducing spatiotemporal datasets and aim for low-latency quantum hardware-in-the-loop learning protocols.

Winner of a competitive German IFB grant (AI-driven imaging data analytics on quantum hardware). The startup is generously supported by "Microsoft for Startups" program. Served as a consultant for European Commission Directorate-General-led studies on Critical Digital Technologies (Photonics), and as principal analyst for a technology advisory firm (ongoing).

• • Theory Division, Center for Free-Electron Laser Science, DESY | Oct 2019 – Present | Research Scientist with Prof. Robin Santra

Developed a quantum theoretical framework for high-energy multiphoton diffractive imaging at synchrotron sources. This technique generalizes previous theories by incorporating the effects of high-order driving and detector photon-field correlations. It allows one to capture many-particle electronic density correlations in finite systems, paving the way for physics-informed learning tasks data analysis of diffraction datasets.

Developed a quantum theoretical framework for single-particle imaging at free-electron laser sources. The resulting theory describes radiation damage, non-equilibrium thermalization, and in-medium interactions within a unified framework. An accurate theory is a prerequisite for the physics-informed deep learning tasks.

• • Theory Division, Max Planck Institute for the Structure and Dynamics of Matter | Sep 2015 – Sep 2019 | Research Associate with Prof. Angel Rubio

Developed a theoretical framework for quantum nonlinear optics with entangled photon sources. Applied this formalism to characterize the ultrafast cavity-QED of molecular vibrations and excitons in light-harvesting complexes. Demonstrated that modulating inter-particle interactions via cavity modes can control quasi-particle wavepackets at femtosecond timescales. This work is considered one of the early theoretical proposals on entangled photon-based 2D spectroscopy of dissipative exciton-polariton dynamics in molecular systems.

Developed Green's function-based numerical simulation protocols for modeling four-wave-mixing (nonlinear response) in general driven-dissipative systems. Designed for scalability and future deep-learning applications, the technique accounts for high-order excitations, structured reservoir modes, and finite laser pulses.

• • University of California, Irvine | Apr 2014 - Aug 2015 | Research Associate with Prof. Shaul Mukamel

Developed a unified quantum framework that combines time-frequency filtered photon coincidence counting and entangled photon driving. The theory allows for the exploration of phonon effects on correlated exciton dynamics over longer timescales. Applied the formalism to the quasiparticle modeling of exciton-phonon dynamics in light-harvesting complexes, demonstrating that narrowband two-exciton wavepackets can be prepared and monitored with high fidelity.

Developed Green's function-based, scalable numerical simulation framework for higher-order exciton dynamics applicable to general driven-dissipative systems. It can evaluate all two-photon counting and two-photon excitations on an equal footing for large molecular systems.

• • Freie Universität Berlin | Jan 2014 - March 2014 & Jun 2009-Aug 2009 | Visiting researcher with Prof. J. C. Tremblay and Prof. Jörn Manz.

Developed a non-Markovian master equation-based numerical simulation framework for the quantum control of adsorbates on metal surfaces. The theory accounts for both non-adiabatic effects from metallic excitations and relaxation effects from acoustic phonons within the same footing. Benchmarking was performed for interacting adsorbates and structured phonon bath at finite temperature.

Developed a numerical framework (based on existing codebase) for time-dependent coupled nuclear-electronic quantum fluxes. Derived key equations. Applied the code to small model systems.

• • Laboratoire collisions agrégats réactivité, CNRS & Université de Toulouse III| Ph.D. in Physics | 2009 – 2013 | France

Dissertation "Control of open quantum systems: Applications to exciton dynamics in quantum dots and vibrational dynamics in carboxyhemoglobin" with with late Prof. Christoph Meier

Developed theoretical frameworks and numerical algorithms for laser pulse-shaping-based quantum control of dissipative systems. Principal contribution was to develop a non-Markovian master equation that scales linearly with the dimension of the system density operator and incorporates laser driving within the non-Markovian memory. Wrote parallelized code tailored for small-sized solid state dissipative systems. Extended the theory to incorporate initial correlation effects. 

Developed an analytical framework which explained role of effects of laser driving on dissipation via finite bandwidth bath. Applied the framework to explain reappearance of coherent oscillations in laser-driven semiconductor quantum dots used for heralded photon sources. This work was first to theoretically predict chirp sign-dependent adiabatic population transfer phenomena in solid state dissipative systems.

Formulated a quantum feed-forward control protocol using laser-driven quantum wavepacket dynamics. The optimization routine generates optimized mid-IR laser pulses for robust population transfer in the presence of fluctuating vibrational modes. Constructed a reduced model from a mixed quantum-classical simulation of a vibrational stretching mode to explain the limits of coherent control. Benchmarked the control mechanism using pump-probe spectra and time-frequency analysis.

Formulated an early proposal merging the variational multiconfigurational Gaussian wavepacket technique with feed-forward control.

Led research collaborations with LPCNO, CNRS, Toulouse, working alongside leading experimentalists. Disseminated research findings at premier international conferences, including RSC Faraday Discussions, CECAM, and FEMTO10. Assisted in evaluating and tutoring MS courses. 

• • Indian Institute of Technology, Guwahati | M.Sc. in Chemistry | 2007 – 2009 | India

Dissertation "Effects of chaotic phase space on high harmonic generation" with Prof. Ashish K. Gupta. 

Developed a phase-space-based semiclassical theory for high-harmonic generation in simplified model systems. Wrote numerical code. 

Distinguished rank-holder in the selection of CSIR, Government of India Fellowship (not pursued). Received Honorable Mention for the Master of Science (MS) dissertation. 

Summer student researcher at Indian Institute of Technology, Kanpur & Indian Association for the Cultivation Science. 

Applied classical phase-space techniques to analyze quantum-classical correspondence in laser-driven bistable systems exhibiting mixed chaotic phase space.

Applied Brillouin-Wigner perturbation theory to estimate solvent-induced perturbations in minimal models describing chemical reactions.

• • University of Calcutta | B.Sc. in Chemistry (Major) with Physics, Mathematics, Statistics | 2004 – 2007 | India

Distinguished rank-holder in Joint Admission Test conducted by Indian Institute of Technologies.

1. A. Debnath. Coherent nonlinear optical probes for cavity-dressed vibrational mode mixing: Multidimensional double-quantum coherence and photon-echo spectroscopy. The Journal of Chemical Physics, 164(24), 2026.

2. A. Debnath and S. Mukamel. Photon entanglement-enhanced multidimensional spectroscopy of exciton correlations in photosynthetic aggregates. The Journal of Chemical Physics, 164(13), 2026. 

3. A. Debnath and R. Santra. Theory of high-energy correlated multiphoton x-ray diffraction. Physical review research, 5(2):023158, 2023.

4. A. Debnath and A. Rubio. Entangled photon assisted multidimensional nonlinear optics of exciton-polaritons. Journal of Applied Physics, 128(11), 2020. 

5. A. Debnath, C. Meier, B. Chatel & T. Amand High-fidelity biexciton generation in quantum dots by chirped laser pulses. Physical Review B, 88(20), 2013.

6. A. Debnath, C. Falvo & C. Meier State-selective excitation of the CO stretch in carboxyhemoglobin by mid-IR laser pulse shaping: a theoretical investigation. The Journal of Physical Chemistry A, 117(48), 2013.

• Co-organizer of Young European Physicist’s Meeting, Toulouse 2011, funded by EU.

TBA