Thanks to the significant advances in quantum technologies, the use of single photon detectors (SPDs) is becoming increasingly common. As a result of the excellent photodetection performance of these detectors, they have been utilized in a wide range of fields such as quantum cryptography, astronomy, spectroscopy, and medical applications. There is no doubt that improvements in the performance of these detectors will open new paths to their multidisciplinary applications. Over the years, several different types of SPDs have been developed, such as photomultiplier tubes based on vacuum tubes, avalanche photodiodes (APDs) based on semiconductors, or nanowires based on superconducting technology. Any of these technologies, which are also commercially offered by many companies, has been used according to their advantages and disadvantages for intended applications by making a trade-off. At that point, SPDs based on Silicon APD technology have many advantages including low voltage operation, high reliability, simple electronic requirements, and high detection efficiency. In this study, the TO-8 SAP500 series Silicon APD provided by Laser Component was preferred, and the driving circuit was designed for visible-range sensing applications. The quenching and thermoelectric cooling circuit designs were presented, and the performance of the detector was analyzed according to some important parameters. Our motivation is to investigate the CubeSat compatibility of the detector for space applications.
Polarization entanglement based cryptography uses the photon pairs generated in a spontaneous paramet- ric down-conversion process and guarantees the security through the violation of Bell’s inequality. Certain experimental parameters affects the entanglement fidelity and leads to a possible information leakage. The optical path difference of photons born at different crystals contributes to reduced fidelity, due to the extra birefringence of the nonlinear crystal. Although previous studies suggested methods to erase the distinguishability of photons by introducing compensation crystals, the phase difference, which is due to the lateral ray distribution is not studied. We used two commercially available collection optics; an aspheric and an achromatic lens. With these collection optics, the effect of collection optics on the entanglement fidelity is studied. We developed a simulation of such a system and found that aspheric collection optics is more suitable to achieve high fidelity.
We present a novel method to measure the range of an object in a lab setting. This is realised by utilizing the phase insensitive cross-correlation analysis of the probe and reference photons generated in a spontaneous parametric down-conversion process. In our technique, the comparative measurement of time-correlated photons after one is transmitted to the target direction and the copy of it retained at the lab allows to single out the signal from the noise lead to sense, range and imaging the sample.
Quantum Radar is a promising technology that could have a strong impact on the civilian and military realms. In this study we introduce a new concept design for implementing a Quantum Radar, based on the time and polarization correlations of the entangled photons for detection and identification and tracking of high-speed targets. The design is focused on extracting high resolution details of the target with precision timing of entangled photons that provides important operational capabilities like distinguishing a target from a decoy. The quantum entanglement properties guarantee the legitimacy of the photons captured by the search telescope. Time correlations of the photon detection events can be extracted via cross-correlation operation between two sets of photon detection time-tags for the entangled photons. The fact that the wavelengths of the entangled photons can be tuned also makes the Quantum Radar concept an enticing candidate for tracking stealth objects. We present the proof-of-principle test results of the Quantum Radar and discuss the technical challenges and limitations of the design.
We report on the performance of a compact photon pair source that was retrieved from a failed space launch. The source had been installed in a nanosatellite and was found to be completely operational upon recovery. Comparison of post-recovery and baseline data suggests that there is no degradation in brightness or polarization correlation between photon pairs. We describe the assembly technique for the robust source. Its survival provides strong evidence that it is possible to design rugged quantum optical systems.
The Small Photon Entangling Quantum System (SPEQS) is an integrated instrument where the pump, photon pair source and detectors are combined within a single optical tray and electronics package. This footprint enables the instrument to be placed onboard nanosatellites or the CubeLab facility within the International Space Station. The first mission to understand the different environmental conditions that may affect the operation of an entangled photon source in low Earth orbit (LEO) is underway. Here we present a work towards a violation of Bell's inequality with a brightness and visibility that can facilitate quantum key distribution (QKD) from space to ground.
To enable space-based quantum key distribution proposals the Centre for Quantum Technologies is developing
a source of entangled photons ruggedized to survive deployment in space and greatly miniaturised so that it
conforms to the strict form factor and power requirements of a 1U CubeSat. The Small Photon Entangling
Quantum System is an integrated instrument where the pump, photon pair source and detectors are combined
within a single optical tray and electronics package that is no larger than 10 cm x 10 cm x 3 cm. This footprint
enables the instrument to be placed onboard nanosatellites or the CubeLab structure aboard the International
Space Station. We will discuss the challenges and future prospects of CubeSat-based missions.
The Small Photon Entangling Quantum System is an integrated instrument where the pump, photon pair source and detectors are combined within a single optical tray and electronics package that is no larger than 10cm×10cm×3cm. This footprint enables the instrument to be placed onboard nanosatellites or the CubeLab facility within the International Space Station. The first mission is to understand the different environmental conditions that may affect the operation of an entangled photon source in low Earth orbit. This understanding is crucial for the construction of cost-effective entanglement based experiments that utilize nanosatellite architecture. We will discuss the challenges and lessons we have learned over three years of development and testing of the integrated optical platform and review the perspectives for future advanced experiments.
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