Atomic spin-controlled non-reciprocal Raman amplification of fibre-guided light

Observation of oscillatory Raman gain associated with two-photon Rabi oscillations of nanofiber-coupled atoms

“…The fit (orange solid line) agrees very well with the data for an effective Rabi frequency of Ω = 2π × 2.63(3) MHz, in reasonable agreement with the estimated Ω = 2π × 2.83 MHz, based on independently calibrated parameters. The fit result Γ = 2π × 516 (21) kHz is in good agreement with the expected value according to Eq. 3, Γ = 2π ×490 kHz.…”

“…This approximation is justified a posteriory by the agreement of our model with the experimental data. Another dephasing mechanism arises from the change of the probe power along the atomic ensemble, which can be accurately modeled by consecutively solving the Lindblad master equation and computing the transmission coefficient of each three-level atom [21]. We numerically checked that our approach captures the dynamics well in the parameter regime studied here.…”

Directional Josephson traveling-wave parametric amplifier via non-Hermitian topology

“…Within the topological bandwidth of w top ∼ 2J = 2π • 310 MHz, the gain is above 13 dB, reverse gain below -23 dB, and noise asymmetry below -22 dB, providing a strong protection to the quantum source that generates the signal. For a directional amplifier, this bandwidth is already one order of magnitude larger than what has been achieved so far [16][17][18][19][20][21], but for practical application it is desirable to provide at least 20 dB of gain over a bandwidth of GHz [15]. We show below that this is possible for a topological JTWPA provided one uses a technique already developed for JPAs.…”

“…We predict that a device with N 30 sites can provide near quantum-limited amplification over a bandwidth of GHz with more than 20 dB of gain and -30 dB of backwards attenuation. This is two orders of magnitude larger in bandwidth and directionality than previous non-reciprocal amplifiers [16][17][18][19][20][21]. Our work thus provides a promising route towards the scalable integration of near-ideal pre-amplifiers and quantum processors on the same on-chip, avoiding the use of external isolators.…”

“…In practice, this is avoided by equipping the JTWPAs with isolators, but these are bulky and lossy external elements that limit the efficiency and scalability of superconducting quantum devices. Directional amplification has only been realized on fewmode non-reciprocal devices [16][17][18][19][20][21], which are fundamentally narrowband. Broadband amplification is crucial towards implementing large-scale quantum information processors, where multiple signals need to be multiplexed and simultaneously detected [22].…”