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Lee D, Pramanik T, Hong S, Cho YW, Lim HT, Chin S, Kim YS. Entangling three identical particles via spatial overlap. OPTICS EXPRESS 2022; 30:30525-30535. [PMID: 36242154 DOI: 10.1364/oe.460866] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2022] [Accepted: 07/22/2022] [Indexed: 06/16/2023]
Abstract
Quantum correlations between identical particles are at the heart of quantum technologies. Several studies with two identical particles have shown that the spatial overlap and indistinguishability between the particles are necessary for generating bipartite entanglement. On the other hand, researches on the extension to more than two-particle systems are limited by the practical difficulty to control multiple identical particles in laboratories. In this work, we propose schemes to generate two fundamental classes of genuine tripartite entanglement, i.e., GHZ and W classes, which are experimentally demonstrated using linear optics with three identical photons. We also show that the tripartite entanglement class decays from the genuine entanglement to the full separability as the particles become more distinguishable from each other. Our results support the prediction that particle indistinguishability is a fundamental element for entangling identical particles.
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Kim I, Lee D, Hong S, Cho YW, Jo Lee K, Kim YS, Lim HT. Implementation of a 3 × 3 directionally-unbiased linear optical multiport. OPTICS EXPRESS 2021; 29:29527-29540. [PMID: 34615061 DOI: 10.1364/oe.436075] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2021] [Accepted: 08/20/2021] [Indexed: 06/13/2023]
Abstract
Linear optical multiports are widely used in photonic quantum information processing. Naturally, these devices are directionally-biased since photons always propagate from the input ports toward the output ports. Recently, the concept of directionally-unbiased linear optical multiports was proposed. These directionally-unbiased multiports allow photons to propagate along a reverse direction, which can greatly reduce the number of required linear optical elements for complicated linear optical quantum networks. Here, we report an experimental demonstration of a 3 × 3 directionally-unbiased linear optical fiber multiport using an optical tritter and mirrors. Compared to the previous demonstration using bulk optical elements which works only with light sources with a long coherence length, our experimental directionally-unbiased 3 × 3 optical multiport does not require a long coherence length since it provides negligible optical path length differences among all possible optical trajectories. It can be a useful building block for implementing large-scale quantum walks on complex graph networks.
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Arbitrary Configurable 20-Channel Coincidence Counting Unit for Multi-Qubit Quantum Experiment. ELECTRONICS 2021. [DOI: 10.3390/electronics10050569] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
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.
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Barros MR, Chin S, Pramanik T, Lim HT, Cho YW, Huh J, Kim YS. Entangling bosons through particle indistinguishability and spatial overlap. OPTICS EXPRESS 2020; 28:38083-38092. [PMID: 33379628 DOI: 10.1364/oe.410361] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Accepted: 11/05/2020] [Indexed: 06/12/2023]
Abstract
Particle identity and entanglement are two fundamental quantum properties that work as major resources for various quantum information tasks. However, it is still a challenging problem to understand the correlation of the two properties in the same system. While recent theoretical studies have shown that the spatial overlap between identical particles is necessary for nontrivial entanglement, the exact role of particle indistinguishability in the entanglement of identical particles has never been analyzed quantitatively before. Here, we theoretically and experimentally investigate the behavior of entanglement between two bosons as spatial overlap and indistinguishability simultaneously vary. The theoretical computation of entanglement for generic two bosons with pseudospins is verified experimentally in a photonic system. Our results show that the amount of entanglement is a monotonically increasing function of both quantities. We expect that our work provides an insight into deciphering the role of the entanglement in quantum networks that consist of identical particles.
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Lee D, Hong S, Cho YW, Lim HT, Han SW, Jung H, Moon S, Lee KJ, Kim YS. Reference-frame-independent, measurement-device-independent quantum key distribution using fewer quantum states. OPTICS LETTERS 2020; 45:2624-2627. [PMID: 32356832 DOI: 10.1364/ol.389440] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2020] [Accepted: 03/29/2020] [Indexed: 06/11/2023]
Abstract
Reference-frame-independent quantum key distribution (RFI-QKD) provides a practical way to generate secret keys between two remote parties without sharing common reference frames. On the other hand, measurement-device-independent QKD (MDI-QKD) offers a high level of security, as it is immune to all quantum hacking attempts to measurement devices. The combination of these two QKD protocols, i.e., RFI-MDI-QKD, is one of the most fascinating QKD protocols, since it holds advantages of both practicality and security. For further practicality of RFI-MDI-QKD, it is beneficial to reduce the implementation complexity. Here, we show that RFI-MDI-QKD can be implemented using fewer quantum states than those of its original proposal. We find that, in principle, the number of quantum states for one of the parties can be reduced from six to three without compromising security. Compared to conventional RFI-MDI-QKD where both parties transmit six quantum states, it significantly simplifies the implementation of the QKD protocol. We also verify the feasibility of the scheme with a proof-of-principle experiment.
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Rojas-Santana JA, Lopez-Mago D. Technical aspects for counting and timing photons with a digital oscilloscope. APPLIED OPTICS 2019; 58:4047-4051. [PMID: 31158158 DOI: 10.1364/ao.58.004047] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2019] [Accepted: 05/02/2019] [Indexed: 06/09/2023]
Abstract
Photon counting and timing are generic tasks in many photonics laboratories. However, the cost of a commercial photon counter system can be a limiting factor to establish a new laboratory. Homemade photon counters can present a cost-saving solution, but they can also present a demanding side project not always part of the main research. Modern digital oscilloscopes are available in most universities and can provide a simple solution to measure photon statistics. Here, we describe the technicalities and limitations for counting and timing photons using a digital oscilloscope.
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Li W, Hu Y, Zhong HS, Wang YF, Wang XL, Peng CZ, Jiang X. Time-tagged coincidence counting unit for large-scale photonic quantum computing. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2018; 89:103113. [PMID: 30399946 DOI: 10.1063/1.5044250] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Accepted: 10/06/2018] [Indexed: 06/08/2023]
Abstract
Real-time analysis of single-photon coincidence is critical in photonic quantum computing. The large channel number and high counting rate foreseen in such experiments pose a big challenge for the conventional time tagged method and coincidence instruments. Here we propose a real-time time-tagged coincidence method and a data filtering solution, demonstrated by a 32-channel coincidence counting unit that has been implemented successfully on a field-programmable gate array system. The unit provides high counting rates, a tunable coincidence window, and a timing resolution of 390 ps. Beyond that, it is feasible to be scaled up to 104 channels and is thus ideally suited for channel consuming applications such as boson sampling. Based on the versatility and scalability the unit has shown, we believe that it is the turn-key solution for many single-photon coincidence counting applications in photonic quantum computing.
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Affiliation(s)
- Wei Li
- Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei 230026, China
| | - Yi Hu
- Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei 230026, China
| | - Han-Sen Zhong
- Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei 230026, China
| | - Yue-Fei Wang
- Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei 230026, China
| | - Xi-Lin Wang
- Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei 230026, China
| | - Cheng-Zhi Peng
- Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei 230026, China
| | - Xiao Jiang
- Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei 230026, China
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Zhang C, Li W, Hu Y, Yang T, Jin G, Jiang X. 48-channel coincidence counting system for multiphoton experiment. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2016; 87:113107. [PMID: 27910666 DOI: 10.1063/1.4967462] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
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.
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Affiliation(s)
- Chen Zhang
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Wei Li
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Yi Hu
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Tao Yang
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Ge Jin
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Xiao Jiang
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
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