Ultrabright Quantum Photon Sources on Chip

Quantum photon sources of high rate, brightness, and purity are increasingly desirable as quantum information systems are quickly scaled up and applied to many fields. Using a periodically poled lithium niobate microresonator on chip, we demonstrate photon-pair generation at high rates of 8.5 and 36.3 MHz using only 3.4 and $13.4\mu \mathrm{W}$ pump power, respectively, marking orders of magnitude improvement over the state of the art, across all material platforms. These results constitute the first direct measurement of the device’s giant single photon nonlinearity. The measured coincidence to accidental ratio is well above 100 at those high rates and reaches $14682\pm 4427$ at a lower pump power. The same chip enables heralded single-photon generation at tens of megahertz rates, each with low autocorrelation $g_H^{(2)}(0)=0.008$ and 0.097 for the microwatt pumps, which marks a new milestone. Such distinct performance, facilitated by the chip device’s noiseless and giant optical nonlinearity, will contribute to the forthcoming pervasive adoption of quantum optical information technologies.

Figure 1

Device design and characterization. (a) Schematic of the PPLN microring. Insets are the scanning electron microscopy images of the fabricated device and an enlargement of the coupling region. (b) and (c) Spectra of IR and visible quasi-${\mathrm{TM}}_{00}$ modes around 1554.6 and 777.3 nm, respectively. Insets are the simulated mode profiles. (d) Temperature dependency of SHG efficiency, with Lorentzian-fitted temperature bandwidth at $1.3°\mathrm{C}$. (e) Absolute SHG efficiency ($P_{sh}/P_p$) versus the on-chip pump power.

Figure 2

Experimental procedures for (a) photon-pair and (b) heralded single-photon generation. Variable attenuator (VA); temperature electronic controller (TEC); beam splitter (BS); time to digital converter (TDC).

Figure 3

(a) Pair generation rate and (b) coincidences-to-accidental ratio and (c) autocorrelation function $g_H^{(2)}(\tau )$ with zero delay time, as the function of on-chip pump power. (d) Heralded idler-idler correlation function $g_H^{(2)}(\tau )$ with antibunching dip of $g_H^{(2)}(0)=0.008\pm 0.0007$ at $3.4\mu \mathrm{W}$ on-chip power. All error bars are estimated by Poissonian photon counting statistics.