Persistent Currents in Half-Moon Polariton Condensates

Abstract

We excite exciton-polariton condensates in half-moon shapes by the non-resonant opti cal excitation of GaAs-based cylindrical pillar microcavities. In this geometry, the 1r-jump of the phase of the condensate wave function coexists with a gradual ±1r phase variation between two horns of the half-moon. We switch between clockwise and counter-clockwise phase currents by slightly shifting the excitation spot on the surface of the pillar. Half moon condensates are expected to reveal features of two-level quantum systems similar to superconducting flux qubits.Among the most well studied states with non-zero OAM are vortex states characterized by the azimuthal phase dependence of the form exp(im0), where the integer mis a quantum num ber frequently referred to as a topological charge [4,5], and nm is the OAM per photon [6], 0 is the azimuthal angle. There exist several approaches for generation of states with non-integer orbital momenta based on the introduction of local phase jumps that make the phase varia tion in the remaining part of the closed loop different from a multiple of 21r. Depending on the physical system under consideration, various approaches are used to create quantum states with the non-integer OAM. For generation of optical fractional vortices one needs specially designed optical elements, fractional vortex lenses or spiral phase plates [7][8][9]. In superfluid ring-shaped Bose-Einstein condensates of ultracold atoms, the method in demand for generating flow states characterized by a phase slip consists in the insertion of a so-called weak link [10,11]. A weak link represents a depletion in the condensate density produced by the external potential barrier moving along the circumference of the condensate at a given velocity. It induces back-scattering for the condensate flows spreading clockwise and counter-clockwise along the ring. This results in interference patterns of the scattered flow states. In recent years, a significant progress in shaping of Bose-Einstein condensates of light-matter quasiparticles, exciton-polaritons, has been reported [12,13]. In contrast to atomic condensates, polariton condensates may be gener ated at relatively high temperatures, including the room temperature [14] that opens the way to their application in classical and quantum information processing.In the present work, creation of polariton phase currents characterised by fractional topolog ical charges is demonstrated by the near-field optical interferometry in cylindrical micropillar microcavities. We experimentally study semiconductor micropillars where the demonstration of concentric circular and lobe condensate patterns [15] and generation of persistent circular currents [16] were reported earlier. We introduce a weak link in a circular polariton condensate that takes a half-moon shape. The polariton density depletion between the horns of the half moon is provoked by the repulsive interaction of the condensate polaritons with the reservoir of incoherent excitons generated by a non-resonant optical excitation und...

Coherence Revivals of a Spinor Polariton Condensate from Self-induced Larmor Precession

“…We attribute this effect to self induced Larmor precession due to polariton interactions and find that the system undergoes more than 10 5 oscillations with surprising stability, despite the effects of gain and dissipation and are fully reproduced with coupled condensate-reservoir mean field theory. It would be interesting to study the temporalmixing of quasi-degenerate (with same principal quantum number n) trapped states that have been proposed, but not experimentally observed, as a pathway towards simulating a flux qubit with polariton condensates [40,41]. Our observations, reveal for the first time that this gain dissipative system in dynamic equilibrium, can display persistent coherent oscillations in the pseudo-spin Bloch sphere for the duration of the quasi-CW optical excitation pulse, in-spite of ultra-fast single particle lifetimes, and opens new interesting applications for polariton condensates such as optical magnetometry [42].…”

Optomechanical tuning of the polarization properties of micropillar cavity systems with embedded quantum dots

“…Our findings can be adapted to other microcavity systems straightforward, for instance to tune spin-orbit coupling [44], which is a crucial component in the construction of photonic topological insulators [45]. Our findings can further be utilized to impact the pseudospin of bosonic condensates of light-matter coupled hybrid systems [46], which currently are gaining interest in the construction of solid-state quantum bits [47].…”

Giant synthetic gauge field for spinless microcavity polaritons in crossed electric and magnetic fields

“…The quantum interference effects in the polariton superfluid are expected to occur in the ring-shaped polariton condensates affected by the perpendicular magnetic and radial electric fields [18,19]. Such a configuration can be realized in the annual optical traps [30] or in a pillar microcavity [24]. Alternatively one can think about constructing of the Berry phase interferometer in the design proposed in [21].…”

“…One of the main reason is the pinning of polarization of polariton condensates in laterally confined structures that suppresses the Berry phase originated from the TE-TM splitting of exciton-polariton modes. The recent works on superfluid circular currents of exciton polaritons in micropillars did not reveal any significant polarizations effects [24]. In this context, it is important to study the topological effects in a scalar (in contrast to spinor) polariton liquid that is devoid of the polarization degree of freedom.…”