Note: Scalable multiphoton coincidence-counting electronics

Arbitrary Configurable 20-Channel Coincidence Counting Unit for Multi-Qubit Quantum Experiment

This paper presents a 20-channel coincidence counting unit (CCU) using a low-end field-programmable gate array (FPGA). The architecture of the CCU can be configured arbitrarily to measure from twofold to twentyfold coincidence counts thanks to a multifold controllable architecture, which can be easily manipulated by a graphical user interface (GUI) program. In addition, it provides up to 20 of each input signal count simultaneously. The experimental results show twentyfold coincidence counts with the resolution occurring in a less than 0.5 ns coincidence window. This CCU has appropriate characteristics for various quantum optics experiments using multi-photon qubits.

Hippopedal intensity plots: drawing comparisons between antenna and optical polarimetry

We present a graphical method for determining the polarization state of light. We review polarization profiling techniques used for antenna systems and correlate them with an optical analog. The analogy is used to perform tabletop optical polarimetry experiments. The experiments require intensity measurements and generation of hippopedal polar plots. The measured polarimetry results are found to agree well with the theoretical predictions. We also set up a cost-effective quantum version of the experiment and reformulate the problem as that of quantum state measurement. These experiments can be incorporated in the teaching laboratory for both classical optics and quantum optics courses, offering a purely quantitative, albeit graphic, technique for polarization analysis. These techniques are already employed for design of microwave antennas; the optic analogy is, therefore, interesting and useful.

48-channel coincidence counting system for multiphoton experiment

In this paper, we demonstrate a coincidence counting system with 48 input channels which is aimed to count all coincidence events, up to 531 441 kinds, in a multiphoton experiment. Using the dynamic delay adjusting inside the Field Programmable Gate Array, the alignment of photon signals of 48 channels is achieved. After the alignment, clock phase shifting is used to sample signal pulses. Logic constraints are used to stabilize the pulse width. The coincidence counting data stored in a 1G bit external random access memory will be sent to the computer to analyze the amount of 2-, 3-, 4-, 5-, and 6-fold coincidence events. This system is designed for multiphoton entanglement experiments with multiple degrees of freedom of photons.

High-performance reconfigurable coincidence counting unit based on a field programmable gate array

We present a high-performance reconfigurable coincidence counting unit (CCU) using a low-end field programmable gate array (FPGA) and peripheral circuits. Because of the flexibility guaranteed by the FPGA program, we can easily change system parameters, such as internal input delays, coincidence configurations, and the coincidence time window. In spite of a low-cost implementation, the proposed CCU architecture outperforms previous ones in many aspects: it has 8 logic inputs and 4 coincidence outputs that can measure up to eight-fold coincidences. The minimum coincidence time window and the maximum input frequency are 0.47 ns and 163 MHz, respectively. The CCU will be useful in various experimental research areas, including the field of quantum optics and quantum information.