BS and MS research

During the midyear semester* of my second year of undergrad, I have decided to apply and join the newly formed research group by Dr. Jayson G. Cosme, who recently finished his Postdoc stint in the University of Hamburg and will join as an Associate Professor in the National Institute of Physics, UP Diliman. It was his mentorship that made me realize the joy of research. At the end of my masters, I have decided to proceed in my journey to become a proper researcher rather than a student, as I have discovered how much I lack and should improve on as a sapling in the field.

My research topics while part of the Theory of Quantum Fluids Group (TQF) includes that of the atom-cavity system and implementation of phase-space methods like the truncated Wigner and positive-P representation. We have dwelve into various interesting dynamical phases such as dissipative time crystals, and the like.

* An academic year is divided into two main semesters, and one midyear. The transition is from first then second semester, and lastly the midyear semester.

BS in Applied Physics

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Abstract

Trapping potential and contact interaction are both frequently overlooked in theoretical predictions but ever-present in atom-cavity experiments. Hence, we examine the influence of harmonic trapping and short-range contact interaction on the nonequilibrium phases in the one-dimensional limit of an atom-cavity system. We solve the equations of motion using a semi-classical method called the truncated Wigner approximation, which incorporates quantum noise in the limit of large number of particles. In this thesis, we consider the \(Z_2\) symmetry breaking of the density wave phase and the lifetime of the dissipative time crystal. We observe that an imbalance in the distribution of the density wave states exists only for sufficiently strong harmonic traps. Furthermore, we find that long-lived dissipative time crystals and a new dynamical phase, metastable dissipative time crystals, exist beyond the idealized limit of the atom-cavity system.

Journal publications

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1. R. J. L. Tuquero, J. Skulte, L. Mathey, J. G. Cosme, Dissipative time crystal in an atom-cavity system: Influence of trap and competing interactions, Phys. Rev. A 105, 043311, (2022). [arXiv]

MS in Physics

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Abstract

Quantum noise is inherent in all quantum systems but is often neglected in theoretical analysis. In this thesis, we plan on investigating the role of inherent quantum noise and other parameters in the dynamics of the phases. To do this, we use a semi-classical method known as phase-space methods such as the truncated Wigner approximation and the positive-P representation. We test the two methods using the Dicke model to explore which method is better suited to the atom-cavity system. Among the dynamical phases, we generally focus on the existence of time crystals. Time crystals are generally classified as either discrete or continuous based on the time translation symmetry being broken. An example of a continuous time crystal is a limit cycle. As such, we explore various parameters such as dissipation, light shift, and presence of trap to the robustness of limit cycles. We also describe the difference of the dynamics for a one- and two-dimensional atom-cavity system. Moreover, we take advantage of the phase-space method by manually turning off stochastic noise to investigate the contribution of noise to the existence of limit cycles. We also present the existence of another limit cycle phase and those characterized by period-doubling instability. Lastly, we showcase the possibility of entrainment from continuous to discrete time crystals in both 1D and 2D.

Journal publications

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1. R. J. L. Tuquero, J. G. Cosme, Impact of quantum noise on phase transitions in an atom-cavity system with limit cycles, Phys. Rev. A 110, 063314, (2024). [arXiv]
2. J. G. Cosme, P. Kongkhambut, A. Bölian, R. J. L. Tuquero, J. Skulte, L. Mathey, A. Hemmerich, H. Keßler, Torus bifurcation of a dissipative time crystal, Phys. Rev. Lett. 134, 223601 (2025). [arXiv]