Robust platform for engineering pure-quantum-state transitions in polariton condensates

We report on pure-quantum-state polariton condensates in optical annular traps. The study of the underlying mechanism reveals that the polariton wave function always coalesces in a single pure quantum state that, counterintuitively, is always the uppermost confined state with the highest overlap with the exciton reservoir. The tunability of such states combined with the short polariton lifetime allows for ultrafast transitions between coherent mesoscopic wave functions of distinctly different symmetries, rendering optically confined polariton condensates a promising platform for applications such as many-body quantum circuitry and continuous-variable quantum processing.

Figure 1

False color-scale experimental (a)–(e) and theoretical (f)–(j) states of polariton condensates. (a),(f) ${\mathrm{\Psi }}_{00}$, (b),(g) ${\mathrm{\Psi }}_{11}$, (c),(h) ${\mathrm{\Psi }}_{01}$, (d),(i) ${\mathrm{\Psi }}_{02}$, and (e),(j) ${\mathrm{\Psi }}_{03}$. $\epsilon$ denotes the ellipticity of individual configurations.

Figure 2

Interference patterns of trapped polariton condensates: (a) ${\mathrm{\Psi }}_{01}$, (b) ${\mathrm{\Psi }}_{02}$, and (c) ${\mathrm{\Psi }}_{03}$. The interference patterns were obtained with a retroreflector configuration.

Figure 3

Evolution of ${\mathrm{\Psi }}_{04}$ for increasing excitation density. Bottom panel: (a) ${\mathrm{\Psi }}_{04}$ at $P=1.03P_{\text{th}}$. (b) Subsequent increase of the power results at the appearance of ${\mathrm{\Psi }}_{05}$. Top panel: Schematic representation of the confined energy states for two different barrier heights. (c) Profiles of the wave function for different excitation densities extracted along the dashed white lines in (a) and (b). (d) Corresponding energy difference with respect to the energy at the coherence threshold for increasing excitation power normalized at the coherence threshold power $P_{\text{th}}$. Inset in (d) shows the spectra of the points denoted by the arrows.

Figure 4

False color-scale real-space tomographic frames in the time domain. (a) ${\mathrm{\Psi }}_{01}$ state at $-30$ ps and (b) subsequent transition to ${\mathrm{\Psi }}_{00}$ at 30 ps. (c) Intensity-normalized time evolution of the emission energy showing the characteristic energy jump at the transition threshold.

Figure 5

Polariton dispersion at $-30$ ps (a), 0 ps, (b), and 30 ps (c). White dotted lines in (a) denote the integrated area from which Fig. 4 was extracted. (d) Schematic representation of the momentum acquired by polaritons tunneling outside the potential trap (potential and dispersion energy not in scale). (e) Intensity-normalized time evolution of $k_x$, showing the characteristic $\mathrm{\Delta }{k}_x$ jump of the tunneling mode.