Quantum computing thread

[SanWenYu]

A recent progress in quantum communication by Prof. Pan and his team.

Paper:

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Free-Space and Fiber-Integrated Measurement-Device-Independent Quantum Key Distribution under High Background Noise​

Measurement-device-independent quantum key distribution (MDI QKD) provides immunity against all attacks targeting measurement devices. It is essential to implement MDI QKD in the future global-scale quantum communication network. Toward this goal, we demonstrate a robust MDI QKD fully covering daytime, overcoming the high background noise that prevents BB84 protocol even when using a perfect single-photon source. Based on this, we establish a hybrid quantum communication network that integrates free-space and fiber channels through Hong-Ou-Mandle (HOM) interference. Additionally, we investigate the feasibility of implementing HOM interference with moving satellites. Our results serve as a significant cornerstone for future integrated space-ground quantum communication networks that incorporate measurement-device-independent security.

News release:

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中国科大实现远距离测量设备无关的自由空间-光纤混合量子密钥分发网络实验

近日，中国科学技术大学潘建伟及其同事彭承志、曹原等与清华大学王向斌，中科院上海微系统所尤立星等人合作，首次在国际上实现了远距离测量设备无关的自由空间-光纤混合量子密钥分发网络实验，并此基础上完成了白天高背景噪声条件和卫星-地面多普勒频移补偿等验证。相关成果于2023年9月6日（北京时间）在线发表在国际学术期刊《物理评论快报》杂志上 [Phys. Rev. Lett. 131, 100802 (2023)]。这项成果全方位验证了星地间测量设备无关量子密钥分发（MDI-QKD）的可行性，向基于卫星的全球化、高安全性量子通信网络迈出了重要一步。

MDI-QKD协议利用双光子干涉技术消除了探测端的所有安全漏洞，无需对测量端的量子设备进行任何安全性假设，被认为是各种量子密钥分发协议中的最佳候选协议之一；而利用自由空间信道和卫星是目前实现全球化量子通信网络的最有效途径。2020年，实验团队通过对独立光源锁频、独立时钟同步、抗强湍流的自适应光学[Opt. Express 28, 36600 (2020); Opt. Express 30, 11684 (2022)] 等技术的发展，在国际上首次将该协议拓展到自由空间信道 [Phys. Rev. Lett. 125, 260503 (2020)]。

在本工作中，实验团队进一步挖掘了MDI-QKD协议的潜能，并探索将其扩展到卫星平台的可行性。为了实现实用化的星地MDI-QKD网络，需要克服自由空间与光纤组网、白天高背景噪声以及多普勒频移等困难。首先，量子干涉测量可作为天然的星型网络节点，非常方便的连接自由空间和光纤信道。实验团队通过构建多个发射端和信道，配合自适应光学技术和单模光纤耦合，演示了自由空间-光纤接口以及星形网络拓扑结构。同时，实验团队首次揭示了基于双光子干涉的符合探测可以使MDI-QKD协议获得极大的容忍背景噪声的能力，实现了正午强烈日光背景下的MDI-QKD实验演示。更近一步，面向星地间存在高速相对运动的情形，实验团队模拟并补偿了卫星过境期间的多普勒频移，将全程的HOM干涉可见度提高到接近理论极限。通过这些实验研究，实验团队全方位验证了星地MDI-QKD的可行性，为未来天地一体、高安全性量子通信网络的构建奠定了坚实基础。

 

[SanWenYu]

Also from USTC on quantum key distribution.

Paper:

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Experimental Demonstration of Fully Passive Quantum Key Distribution​

The passive approach to quantum key distribution (QKD) consists of removing all active modulation from the users’ devices, a highly desirable countermeasure to get rid of modulator side channels. Nevertheless, active modulation has not been completely removed in QKD systems so far, due to both theoretical and practical limitations. In this Letter, we present a fully passive time-bin encoding QKD system and report on the successful implementation of a modulator-free QKD link. According to the latest theoretical analysis, our prototype is capable of delivering competitive secret key rates in the finite key regime.

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中国科大实现全被动量子密钥分发

我校郭光灿院士团队在量子密钥分发研究中取得重要进展。该团队韩正甫、王双、银振强、陈巍与合作者提出了一种无需主动调制的新型量子密钥分发实现方案并完成了实验验证，为实现高现实安全的量子密钥分发系统提供了新思路。该成果于2023年9月13日发表在国际学术期刊《Physical Review Letters》[Phys. Rev. Lett. 131, 110802 (2023)]。

量子密钥分发理论上可以实现无条件安全的密钥共享。但器件特性、调制精度、环境干扰等因素有可能造成系统的现实安全性问题。例如，郭光灿团队发现，系统中广泛使用的铌酸锂主动调制器件，可能会受到光折变等侧信道攻击而泄漏信息[Optica, 10, 520-527(2023)][Phys. Rev. Applied, 19,054052(2023)]。

为彻底解决主动调制带来的隐患，郭光灿团队与合作者另辟蹊径，设计了无需主动调制的量子密钥分发系统。该系统方案克服了此前无法同时实现“被动”光强调制和量子态编码的矛盾，并给出了考虑“有限长效应”的严格安全密钥率。团队通过全被动时间戳-相位编码解决信道环境干扰的难题，同时通过优化后选择策略解决数据吞吐量过大的难题，最终完成了无需任何主动调制的量子密钥分发系统，验证了全被动量子密钥分发的安全性与可行性。

安全性是量子密钥分发的核心价值和要求。探索具有更高现实安全性的协议，并设计相应的方案和系统，是推进量子密钥分发走向实用化的关键之一。该研究为实现高现实安全的量子密钥分发系统提供了全新的思路，对推动该领域的实用化和标准化具有重要意义。

 

[olalavn]

China's first attosecond laser device is under construction in Dongguan, providing strong impetus for breakthroughs in many major basic scientific issues such as quantum computing.

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[tphuang]

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Jiuzhang-3 photonic QC with 255 photons have been created and tested with Boson sample problems. I'm not actually sure it makes that much sense in just comparing its speed to this very specific problem when it can't be used for that many real world computations yet. I do hope that changes soon

 

[luminary]

The answer is obvious once you think about it.

Having unhackable systems would prevent the NSA from spying on their own citizens and allies. This would be completely unacceptable to the hegemon.

The US is not going to do any research on QC (at least publicly) and in the future will likely ban quantum communication systems on national security grounds. They might even create a fake QC system, the same way the US has fake 5G to prevent people from complaining.

lo and behold:

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Quantum computers may soon be able to crack encryption methods in use today, so plans are already under way to replace them with new, secure algorithms. Now it seems the US National Security Agency may be undermining that process.

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at the University of Illinois Chicago says that the US National Institute of Standards and Technology (NIST) is deliberately obscuring the level of involvement the US National Security Agency (NSA) has in developing new encryption standards for “post-quantum cryptography” (PQC). He also believes that NIST has made errors – either accidental or deliberate – in calculations describing the security of the new standards.

Bernstein alleges that NIST’s calculations for one of the upcoming PQC standards, Kyber512, are “glaringly wrong”, making it appear more secure than it really is.

 

[CMP]

lo and behold:

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Quantum computers may soon be able to crack encryption methods in use today, so plans are already under way to replace them with new, secure algorithms. Now it seems the US National Security Agency may be undermining that process.

So what you are telling me is if China can build all their own encryption from the ground up, China will be able to hack the shit out of the US but the US will not be able to do the reverse to China?

 

[sunnymaxi]

China has made a breakthrough in cooling capabilities of quantum systems, with a dilution refrigerator independently developed by a Chinese company rolling off production line recently.

Such refrigerators can provide an ultra-low temperature environment close to absolute zero.

Source - @Chinascience

 

[gadgetcool5]

An obscure U.S. startup, Atom Computing, has defeated the big boys like Google & IBM and (any Chinese entity) to become the first to create a 1,000 qubit quantum computer!

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The record-breaking machine from California-based start-up Atom Computing, which has 1180 qubits, uses neutral atoms trapped by lasers in a 2-dimensional grid.

One advantage of this design is that it is easy to scale up the system and add many more qubits into the grid, says

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, CEO of Atom Computing. Any useful quantum computer in the future that is free of errors, a feature called fault tolerance, will need at least tens of thousands of dedicated error-correcting qubits working alongside the programmable qubits, he says.

 

[SanWenYu]

Prof. Pan and his coworkers built a device independent quantum randomness service that generates and publicly broadcasts true random numbers certified by loophole-free Bell test and signed in postquantum cryptography. With this randomness service, they implemented noninteractive zero-knowledge proof (NIZKP) of the three-coloring problem as a proof of concept.

NIZKP allows one of two anonymous parties to trust a statement of the other, without interaction (i.e. handshakes of any kind) or the other to reveal any additional info. The proof of the statement is based on a hash function. This work enhances security of NIZKP with the true randomness.

Omitting the handshake makes NIZKP more efficient than interactive ZKP. Network protocals using NIZKP can thus support much greater secure traffic. Perhaps a practical application of this work of Prof. Pan will be in the digial yuan wallets.

Paper:

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Device-independent quantum randomness–enhanced zero-knowledge proof​

Significance​

The noninteractive zero-knowledge proof (NIZKP) is underlying a broad spectrum of applications. The major categories of NIZKP are instantiated with deterministic hash functions in the real world. However, the outputs of deterministic hash functions are modeled as truly random. Thus, this unrealizable assumption potentially undermines the security of the protocol. In this work, we bring quantumness to the table: We remove the assumption in NIZKP by implementing a quantum randomness service. We demonstrate the service in a proof-of-principle experiment, which publicly broadcasts random numbers based on quantum nonlocality and signed by postquantum cryptography (PQC). By bridging together quantum nonlocality, PQC, and Zero-knowledge proof, we anticipate this work to inspire more innovative applications that combine quantum information and cryptography.

Abstract​

Zero-knowledge proof (ZKP) is a fundamental cryptographic primitive that allows a prover to convince a verifier of the validity of a statement without leaking any further information. As an efficient variant of ZKP, noninteractive zero-knowledge proof (NIZKP) adopting the Fiat–Shamir heuristic is essential to a wide spectrum of applications, such as federated learning, blockchain, and social networks. However, the heuristic is typically built upon the random oracle model that makes ideal assumptions about hash functions, which does not hold in reality and thus undermines the security of the protocol. Here, we present a quantum solution to the problem. Instead of resorting to a random oracle model, we implement a quantum randomness service. This service generates random numbers certified by the loophole-free Bell test and delivers them with postquantum cryptography (PQC) authentication. By employing this service, we conceive and implement NIZKP of the three-coloring problem. By bridging together three prominent research themes, quantum nonlocality, PQC, and ZKP, we anticipate this work to inspire more innovative applications that combine quantum information science and the cryptography field.

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我科学家实现基于器件无关量子随机数信标的零知识证明​

记者8日从中国科学技术大学获悉，该校潘建伟院士、张强教授等与国内研究者合作，首次实现了一套以器件无关量子随机数产生器作为熵源，以后量子密码作为身份认证的随机数信标公共服务，将其应用到零知识证明（ZKP）领域中，消除了非交互式零知识证明（NIZKP）中实现真随机数的困难所带来的安全隐患，提高了NIZKP的安全性。相关成果日前发表于国际学术期刊《美国国家科学院院刊》。

零知识证明是一种基本的密码学工具，允许互不信任的通信双方之间，一方向另一方证明某个命题的有效性，同时不泄露任何额外信息。NIZKP是ZKP的一种最重要的变体，其特点是通信双方无需多次信息交换。由于其简单易行并且互相通信次数少，NIZKP广泛应用于数字签名、区块链和身份认证等领域。常用的NIZKP系统的安全性建立在生成可信的真随机数的假设之上，然而，由于真随机数生成器难以实现，实际应用中常会使用确定性的伪随机数算法来替代，这种方法会产生潜在的安全隐患。

量子物理学中，基于无漏洞贝尔不等式检验的器件无关量子随机数（DIQRNG）可以提供具有最高安全等级的真随机数，其安全性由量子力学基本原理保证，无需用户对量子设备进行任何先验表征或假设。

在前期工作基础上，研究团队搭建了一个基于DIQRNG的信标公共服务系统，并利用该系统设计并实施了一种不依赖于真随机数假设的NIZKP方案。该随机数信标服务可以实时向公众广播生成的随机数。此外，为确保随机数在广播过程中的安全性，研究团队采用了可以抵御量子攻击的量子安全签名算法。随后，研究团队利用接收到的来自DIQRNG的随机数代替之前的伪随机数，构建并实验验证了更安全的NIZKP协议。

该研究成果首次将量子非局域性、量子安全算法和零知识证明三个不同的领域结合起来，大幅提升了零知识证明的安全性，其中构建的面向公众的随机数服务在密码学、彩票业和社会公益等领域有着重要的潜在应用。

 

[horse]

An obscure U.S. startup, Atom Computing, has defeated the big boys like Google & IBM and (any Chinese entity) to become the first to create a 1,000 qubit quantum computer!

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The record-breaking machine from California-based start-up Atom Computing, which has 1180 qubits, uses neutral atoms trapped by lasers in a 2-dimensional grid.

One advantage of this design is that it is easy to scale up the system and add many more qubits into the grid, says

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, CEO of Atom Computing. Any useful quantum computer in the future that is free of errors, a feature called fault tolerance, will need at least tens of thousands of dedicated error-correcting qubits working alongside the programmable qubits, he says.

Does this thing even work?

Seriously, it has to compute something. If it only measures the amount of qbits, that is just a good experiment.