Browsing by Author "Chaiwongkhot P."

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    Boosting End-to-End Entanglement Fidelity in Quantum Repeater Networks via Hybridized Strategies
    (2024-01-01) Pathumsoot P.; Tansuwannont T.; Benchasattabuse N.; Satoh R.; Hajdusek M.; Chaiwongkhot P.; Suwanna S.; Van Meter R.; Pathumsoot P.; Mahidol University
    Quantum networks are expected to enhance distributed quantum computing and quantum communication over long distances while providing security dependent upon physical effects rather than mathematical assumptions. Through simulation, we show that a quantum network utilizing only entanglement purification or only quantum error correction as error management strategies cannot create Bell pairs with fidelity that exceeds the requirement for a secured quantum key distribution protocol for a broad range of hardware parameters. We propose hybrid strategies utilizing quantum error correction on top of purification and show that they can produce Bell pairs of sufficiently high fidelity. We identify the error parameter regime for gate and measurement errors in which these hybrid strategies are applicable.
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    Faking photon number on a transition-edge sensor
    (2022-12-01) Chaiwongkhot P.; Zhong J.; Huang A.; Qin H.; Shi S.c.; Makarov V.; Mahidol University
    We study potential security vulnerabilities of a single-photon detector based on superconducting transition-edge sensor. In one experiment, we show that an adversary could fake a photon number result at a certain wavelength by sending a larger number of photons at a longer wavelength, which is an expected and known behaviour. In another experiment, we unexpectedly find that the detector can be blinded by bright continuous-wave light and then, a controlled response simulating single-photon detection can be produced by applying a bright light pulse. We model an intercept-and-resend attack on a quantum key distribution system that exploits the latter vulnerability and, under certain assumptions, able to steal the key.
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    Hybrid Quantum-Classical Algorithms for Loan-Collection Optimization with Loan-Loss Provisions
    (2023-06-01) Tangpanitanon J.; Saiphet J.; Palittapongarnpim P.; Chaiwongkhot P.; Prugsanapan P.; Raksasri N.; Wannasiwaporn W.; Raksri Y.; Thajchayapong P.; Chotibut T.; Mahidol University
    Banks are required to set aside funds in their income statement, known as a loan-loss provision (LLP), to account for potential loan defaults and expenses. By treating the LLP as a global constraint, we propose a hybrid quantum-classical algorithm to solve a specific case of quadratic constrained binary optimization (QCBO) models for loan-collection optimization. The objective is to find a set of optimal loan-collection actions that maximizes the expected net profit presented to the bank as well as the financial welfare in the financial network of loanees, while keeping the LLP at its minimum. Our algorithm consists of three parts: a classical divide-and-conquer algorithm to enable a large-scale optimization, a quantum alternating operator ansatz (QAOA) algorithm to maximize the objective function, and a classical sampling algorithm to handle the LLP. We apply the algorithm to a real-world data set with 600 loanees and five possible collection actions. The QAOA is performed using up to 35 qubits on a classical computer. We show that incorporating the QAOA can enhance the expected net profit by approximately 70% in comparison to scenarios where the QAOA is absent from the hybrid algorithm. Although this improvement does not constitute definitive evidence of quantum advantage, our work illustrates the use of near-term quantum devices to tackle real-world optimization problems.
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    Measurement of sparse vs. dense atmospheric secondary particles from cosmic ray showers using coincident signals on various counters in a neutron monitor
    (2024-09-27) Chaiwongkhot K.; Ruffolo D.; Sáiz A.; Mitthumsiri W.; Chaiwongkhot P.; Banglieng C.; Mangeard P.S.; Evenson P.; Lakronwat J.; Chaiwongkhot K.; Mahidol University
    For the Princess Sirindhorn Neutron Monitor in Thailand, we find that the cross-counter leader fraction (XLF), i.e., inverse of multiplicity across counters, depends on counter separation and differs for end and middle counter tubes. Multiplicity at small separation can be attributed to single secondary particles, while multiplicity at large separation indicates multiple secondaries from the same cosmic ray shower. The end/middle differences are clarified using follow-up measurements of 1) analog neutron signals from selected counters and 2) digital timing data from all counters for events of interest. Considering Counters 17 and 18 at the edge of the monitor, triggering on either counter leads to the same event rate on the other, so small-separation XLF depends on the count rate of the first (triggering) counter, which is lower for an end counter. To examine large-separation multiplicity, due to multiple secondaries, an FPGA-based readout system was triggered by Counter 2 followed by Counter 18 within 250 microseconds, while also monitoring Counter 10 in between. Counter 10 exhibited an enhanced rate, indicating a few events that densely “carpeted” the neutron monitor, but the majority of triggers involved a sparse distribution of isolated secondary particles. This is consistent with the digital timing data from all counters and end/middle differences in XLF.
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    Preparing a commercial quantum key distribution system for certification against implementation loopholes
    (2024-10-01) Makarov V.; Abrikosov A.; Chaiwongkhot P.; Fedorov A.K.; Huang A.; Kiktenko E.; Petrov M.; Ponosova A.; Ruzhitskaya D.; Tayduganov A.; Trefilov D.; Zaitsev K.; Makarov V.; Mahidol University
    A commercial quantum key distribution (QKD) system needs to be formally certified to enable its wide deployment. The certification should include the system's robustness against known implementation loopholes and attacks that exploit them. Here we ready a fiber-optic QKD system for this procedure. The system has a prepare-and-measure scheme with decoy-state BB84 protocol, polarization encoding, a qubit source rate of 312.5 MHz, and is manufactured by QRate. We detail its hardware and postprocessing. We analyze the hardware for known implementation loopholes, search for possible new loopholes, and discuss countermeasures. We then amend the system design to address the highest-risk loopholes identified. We also work out technical requirements on the certification lab and outline its possible structure.
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    Protecting Fiber-Optic Quantum Key Distribution Sources against Light-Injection Attacks
    (2022-10-01) Ponosova A.; Ruzhitskaya D.; Chaiwongkhot P.; Egorov V.; Makarov V.; Huang A.; Mahidol University
    A well-protected and characterized source in a quantum key distribution system is needed for its security. Unfortunately, the source is vulnerable to light-injection attacks, such as Trojan-horse, laser-seeding, and laser-damage attacks, in which an eavesdropper actively injects bright light to hack the source unit. The hacking laser could be a high-power one that can modify properties of components via the laser-damage attack and also further help the Trojan-horse and other light-injection attacks. Here we propose a countermeasure against the light-injection attacks, consisting of an additional sacrificial component placed at the exit of the source. This component should either withstand high-power incoming light while attenuating it to a safe level that cannot modify the rest of the source, or get destroyed into a permanent high-attenuation state that breaks up the line. We demonstrate experimentally that off-the-shelf fiber-optic isolators and circulators have these desired properties, at least under attack by a continuous-wave high-power laser.
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    Resilience of Quantum Key Distribution Source against Laser-Damage Attack by a Variety of Lasers
    (2023-01-01) Ruzhitskaya D.; Zhluktova I.; Ponosova A.; Trefilov D.; Chaiwongkhot P.; Huang A.; Kamynin V.; Makarov V.; Ruzhitskaya D.; Mahidol University
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    Resilience of Quantum Key Distribution Source against Laser-Damage Attack by a Variety of Lasers
    (2023-01-01) Ruzhitskaya D.; Zhluktova I.; Ponosova A.; Trefilov D.; Chaiwongkhot P.; Huang A.; Kamynin V.; Makarov V.; Mahidol University
    Quantum key distribution (QKD) systems provide quantum-safe key exchange. Therefore, complete security analysis of implementations of QKD protocols is in the focus of interest of a worldwide information-security community. For today, a number of QKD loopholes are closed by countermeasures, which are also considered in emerging QKD security evaluation and certification [1-3]. However, new threats to practical QKD implementations are still found, such as the laser-damage attack, which is a powerful hacking strategy. In investigations, CW laser radiation is most often used, but in contrast to it, the interaction of pulsed laser radiation with optical materials may lead to a wide range of effects, like nonlinear effects, dielectric breakdown, etc.