ABSTRACT
We designed a dual-wavelength photon-counting laser interferometer for absolute distance measurement of noncooperative targets. The weak optical interference on the rough surface was measured by a single-photon detector. The range of nonambiguity of the dual-wavelength interferometer was less than 1.2 µm, as the maximum errors of Lg and Lr were 7.8 nm and 9.1 nm caused by the photon-counting measurement and the frequency shift of the two unlocked lasers. We integrated laser triangulation into the interferometer as a coarse measurement, thus increasing the range of nonambiguity to 6.5 mm. As a result, a measurement standard deviation of â¼18 nm was achieved within a range of 1.1 mm in the experiment.
ABSTRACT
The exquisite optical and spin properties of nitrogen-vacancy (NV) centers in diamond have made them a promising platform for quantum sensing. The prospect of NV-based sensors relies on the controlled production of these atomic-scale defects. Here we report on the fabrication of a preferentially oriented, shallow ensemble of NV centers and their applicability for sensing dc magnetic fields. For the present sample, the residual paramagnetic impurities are the dominant source of environmental noise, limiting the dephasing time (T2*) of the NVs. By controlling the P1 spin-bath, we achieve a 4-fold improvement in the T2* of the NV ensemble. Further, we show that combining spin-bath control and homonuclear decoupling sequence cancels NV-NV interactions and partially protects the sensors from a broader spin environment, thus extending the ensemble T2* up to 10 µs. With this decoupling protocol, we measure an improved dc magnetic field sensitivity of 1.2 nT µm3/2 Hz-1/2. Using engineered NVs and decoupling protocols, we demonstrate the prospects of harnessing the full potential of NV-based ensemble magnetometry.
ABSTRACT
We report on a high-speed temporal and spatial multiplexed single-photon counter with photon-number-resolving capability up to four photons. The infrared detector combines a fiber loop to split, delay and recombine optical pulses and a 200 MHz dual-channel single-photon detector based on InGaAs/InP avalanche photodiode. To fully characterize the photon-number-resolving capability, we perform quantum detector tomography and then reconstruct its positive-operator-valued measure and the associated Wigner functions. The result shows that, despite of the afterpulsing noise and limited system detection efficiency, this temporal and spatial multiplexed single-photon counter can already find applications for large repetition rate quantum information schemes.
ABSTRACT
We experimentally presented a full quantum detector tomography of a synchronously pumped infrared single-photon frequency upconversion detector. A maximum detection efficiency of 37.6% was achieved at the telecom wavelength of 1558 nm with a background noise about 1.0 × 10-3 counts/pulse. The corresponding internal quantum conversion efficiency reached as high as 84.4%. The detector was then systematically characterized at different pump powers to investigate the quantum decoherence behavior. Here the reconstructed positive operator valued measure elements were equivalently illustrated with the Wigner function formalism, where the quantum feature of the detector is manifested by the presence of negative values of the Wigner function. In our experiment, pronounced negativities were attained due to the high detection efficiency and low background noise, explicitly showing the quantum feature of the detector. Such quantum detector could be useful in optical quantum state engineering, quantum information processing and communication.
ABSTRACT
We demonstrated a time-of-flight (TOF) ranging system employing laser pulses at 1550 nm with multiple repetition rates to decrease the range ambiguity, which was usually found in high-repetition TOF systems. The time-correlated single-photon counting technique with an InGaAs/InP avalanche photodiode based single-photon detector, was applied to record different arrival time of the scattered return photons from the non-cooperative target at different repetition rates to determine the measured distance, providing an effective and convenient method to increase the absolute range capacity of the whole system. We attained hundreds of meters range with millimeter accuracy by using laser pulses of approximately 10-MHz repetition rates.
ABSTRACT
We investigated the photon-number-resolving (PNR) performance of the InGaAs/InP avalanche photodiode (APD) as a function of the electric gate width and the photon arrival time. The optimal electric gate width was around 1 ns for PNR measurements in our experiment, which provided a PNR capability up to three photons per pulse when the detection efficiency was ~20%. And the dependence of the PNR performance on the arrival time of the photons showed that the photon number could be better resolved if the photons arrived on the rising edge of the electric gate than on the falling edge. In addition, we found that with the increase of the electric gate width, PNR performance got worse. The observation would be helpful for improving the PNR performance of the InGaAs/InP APD in the gated mode.
Subject(s)
Arsenicals/chemistry , Gallium/chemistry , Indium/chemistry , Phosphines/chemistry , Photometry/instrumentation , Semiconductors , Equipment Design , PhotonsABSTRACT
A low-noise high-speed InGaAs/InP-based single-photon detector was demonstrated with a double-self-differencing spike signal cancellation technique. A photon-number resolving method was used to analyze the ratio of avalanche signal to background noise. By adding a post-self-differencing circuit to the pre-self-differencing circuit, the signal to noise ratio was improved by 11.0 dB. The typical error count probability was as low as 2.1% and 6.4% at the detection efficiency of 20.6% and 30.5%, respectively.
