Dipolar Electromagetic Condensate

[Harry Costas]

Dipolar condensates

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[Harry Costas]

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[Harry Costas]

[Submitted on 1 Jul 2025]

Fractional Shapiro steps in a Cavity-Coupled Josephson ring condensate​

Nalinikanta Pradhan, Rina Kanamoto, M. Bhattacharya, Pankaj Kumar Mishra

The Josephson effect presents a fundamental example of macroscopic quantum coherence as well as a crucial enabler for metrology (e.g. voltage standard), sensing (e.g. Superconducting Quantum Interference Device) and quantum information processing (Josephson qubits). Recently, there has been a major renewal of interest in the effect, following its observation in Bose, Fermi, and dipolar atomic condensates, in exciton-polariton condensates, and in momentum space. We present theoretically a nondestructive, \textit{in situ} and real time protocol for observing the AC and DC Josephson effects including integer (recently observed in cold atoms) and fractional (hitherto unobserved in cold atoms) Shapiro steps, using a ring condensate coupled to an optical cavity. Our analysis presents a metrology standard that does not require measurmement of atomic number and that challenges the conventional wisdom that quantum computations cannot be observed without being destroyed. Our results have implications for the fields of atomtronics, sensing, metrology and quantum information processing.

 

[Harry Costas]

[Submitted on 3 Jul 2025]

Analytic Phase Solution and Point Vortex Model for Dipolar Quantum Vortices​

Ryan Doran, Thomas Bland

We derive an analytic expression for the phase of a quantum vortex in a dipolar Bose-Einstein condensate, capturing anisotropic effects from long-range dipole-dipole interactions. This solution provides a foundation for a dipolar point vortex model (DPVM), incorporating both phase-driven flow and dipolar forces. The DPVM reproduces key features of vortex pair dynamics seen in full simulations, including anisotropic velocities, deformed orbits, and directional motion, offering a minimal and accurate model for dipolar vortex dynamics. Our results open the door to analytic studies of vortices in dipolar quantum matter and establish a new platform for exploring vortex dynamics and turbulence in these systems.

 

[Harry Costas]

[Submitted on 14 Jul 2025]

Hollow cylindrical droplets in a very strongly dipolar condensate​

S. K. Adhikari

A harmonically trapped Bose-Einstein condensate (BEC) leads to topologically trivial compact states. Because of the long-range nonlocal dipole-dipole interaction, a strongly dipolar BEC revealed many novel phenomena. Here we show that in a strongly dipolar BEC one can have a hollow cylindrical quasi-one-dimensional metastable droplet with ring topology while the system is trapped only in the x-y plane by a harmonic potential and a Gaussian hill potential at the center and untrapped along the polarization z axis. In this numerical investigation we use the imaginary-time propagation of a mean-field model where we include the Lee-Huang-Yang interaction, suitably modified for dipolar systems. Being metastable, these droplets are weakly stable and we use real-time propagation to investigate its dynamics and establish stability.