Quantum advantage for probabilistic one-time programs

Quantum Machine Learning (QML) approaches introduce unique computational requirements that continuously emerge, from data encoding to model training, from data preparation to model deployment, thus spanning a wide range of possible scenarios. In contrast with classical machine learning, they require dynamic coordination of classical and quantum resources, such as the choice between real quantum processing units or simulators. Unfortunately, traditional MLOps frameworks, built around classical ML workflows, fail to accommodate this dynamic need for quantum resources throughout the pipeline. To address this limitation, we propose an MLOps framework that leverages cloud-native infrastructure, based on container orchestration, to support quantum-classical ML workflows, with dynamic allocation of quantum and classical resources, computational paradigm-agnostic orchestration, and flexible workflow management. These foundational factors unlock the potential of quantum machine learning through elastic hybrid architectures. Built on top of Kubernetes, our framework enables flexible allocation of quantum resources at any stage, without disrupting classical MLOps workflows and, consequently, ensuring traditional peculiarities, such as data and model versioning. This framework we design ensures consistent operations and fosters reproducibility across hybrid environments under a single infrastructure, hence providing a guiding framework for future-ready quantum-classical machine learning systems.

The basics of logic programming, as embodied by Prolog, are generally well-known in the programming language community. However, more advanced techniques, such as tabling, answer subsumption and probabilistic logic programming fail to attract the attention of a larger audience. The cause for the community's seemingly limited interest lies with the presentation of these features: the literature frequently focuses on implementations and examples that do little to aid the understanding of non-experts in the field. The key point is that many of these advanced logic programming features can be characterised in more generally known, more accessible terms. In my research I try to reconcile these advanced concepts from logic programming (Tabling, Answer subsumption and probabilistic programming) with concepts from functional programming (effects, monads and applicative functors).

Probabilistic programming refers to the idea of using standard programming constructs for specifying probabilistic models from machine learning and statistics, and employing generic inference algorithms for answering various queries on these models, such as posterior inference and estimation of model evidence. Although this idea itself is not new and was, in fact, explored by several programming-language and statistics researchers in the early 2000, it is only in the last few years that probabilistic programming has gained a large amount of attention among researchers in machine learning and programming languages, and that expressive and efficient probabilistic programming systems (such as Anglican, Church, Figaro, Infer.net, PSI, PyMC, Stan, and Venture) started to appear and have been taken up by a nontrivial number of users. The primary goal of my talk is to introduce probabilistic programming to the CONCUR/QUEST/FORMATS audience. At the end of my talk, I want the audience to understand basic results and techniques in probabilistic programming and to feel that these results and techniques are relevant or at least related to what she or he studies, although they typically come from foreign research areas, such as machine learning and statistics. My talk will contain both technical materials and lessons that I learnt from my machine-learning colleagues in Oxford, who are developing a highly-expressive higher-order probabilistic programming language, called Anglican. It will also include my work on the denotational semantics of higher-order probabilistic programming languages and their inference algorithms, which are jointly pursued with colleagues in Cambridge, Edinburgh, Oxford and Tubingen.

Quantum cybersecurity is the study of all facets regarding the security of communication and computation in a distributed network. Significant developments in quantum technologies have outclassed their classical counterparts, thus envisioning the realization of a quantum internet. However, such quantum resources, in the hands of an adversary, can jeopardize network security. In this paper, we study two secure network connectivity concerns, namely, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">privacy</i> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">anonymity</i> , in quantum information retrieval systems. To this end, we propose a state-of-the-art single-server multi-user quantum anonymous private information retrieval (QAPIR) protocol. To actualize this, we utilize anonymous entanglement as a quantum resource. We show that the QAPIR protocol not only provides privacy but also introduces anonymity as an added layer of security in quantum networks. Furthermore, we also detail a comparative security analysis that establishes the desirable properties of our proposal.

<title>Abstract</title> Variational Quantum Classifiers are hybrid algorithms with parameterized circuits, that replicate the neural network structure using both quantum and classical resources. Feature map and Ansatz (parameterized circuit) are the major parts of the algorithm for embedding classical data into quantum states and creating a suitable state that minimizes the cost function with the update of parameters, respectively. The number of times the feature map and the Ansatz are applied in the circuit, greatly affects the accuracy. We propose the optimal number of repetitions of the feature map and Ansatz that will help drive the maximum advantage out of VQCs. With the right combination of repetitions, one can fine-tune the model better.

Quantum state engineering and state characterization is a key task in quantum information processing in both discrete and continuous variable systems in the optical domain. In particular, quantum states with non-Gaussian (i.e., non-positive) Wigner quasiprobability distribution functions are crucial to universal, fault-tolerant quantum computing with continuous variables. In this talk, we present our recent results on single-photon Fock state tomography using Photon-Number-Resolving (PNR) measurements. We generated a highly pure narrow-band single-photon Fock state by heralding cavity-enhanced spontaneous-parametric-downconversion from a PPKTP optical parametric oscillator. The Wigner function was reconstructed with photon statistics obtained using superconducting transition-edge sensors with an overall system efficiency of 58(2)%. We then discuss quantum state engineering for pure displaced single-photon Fock states, optical cat states, and approximate GKP states using coherent states and single-photon states along with linear optics and PNR measurements. We report our experimental progress for the same.

We present a theoretical study of the interferences between hybrid single-photon state, coherent state, and vacuum state in the designed medium of a six-ports Mach-Zehnder Interferometer (6p-MZI). The hybrid three different quantum states were simultaneously injected into the input ports of the interferometer. The derivation result demonstrated that the output state showed the statistical blend states among a substituted single-photon state, coherent state, and vacuum state. Interestingly, our calculation results attested that the maximum probability of detected photons at the individual interferometer output ports were significantly dependents on the amplitude of the inputted coherent state.

Encoding and processing quantum information in the time-of-arrival of photons offer significant advantages for quantum information science and technology. These advantages include ease of experimental realization, robustness over photon state transmission, and compatibility with existing telecommunication infrastructure. Additionally, time-of-arrival encoding has the potential for high-rate quantum communication and holds promise for the future development of quantum internet. This review explores the generation, processing, and applications of time-encoded quantum states, focusing on both single-photon states, energy–time entanglement, and time-bin entanglement. We summarize the nonlinear optics platforms and advanced laser and modulation techniques utilized for photon sources that enable quantum information encoding onto the photons' time-of-arrival. We also highlight advanced quantum state processing methods in the time domain, including the Franson interferometry, optical switch-based schemes, and state-of-the-art measurement and detection schemes that allow for high-speed and multi-dimensional quantum operations. Finally, we review the mainstream implementations mainly including the quantum communication demonstrations and outline future directions for developing practical quantum networks leveraging time-encoded photon states.

Quantum state transmission is a prerequisite for various quantum communication networks. The channel noise inevitably introduces distortion of quantum states passing through either a free-space channel or a fibre channel, which leads to errors or decreases the security of a practical quantum communication network. Quantum error rejection is a useful technology to faithfully transmit quantum states over large-scale quantum channels. It provides the communication parties with an uncorrupted quantum state by rejecting error states. Usually, additional photons or degrees of freedom are required to overcome the adverse effects of channel noise. As quantum error rejection method consumes less quantum resource than other anti-noise methods, it is more convenient to perform error-rejection quantum state transmission with current technology. In this review, several typical quantum error-rejection schemes for single-photon state transmission are introduced in brief and some error-rejection schemes for entanglement distribution are also briefly presented.

Classical and quantum technologies have traditionally been viewed as orthogonal, with classical systems being deterministic and quantum systems inherently probabilistic. This distinction hinders the development of a scalable quantum internet even as the global internet continues expanding. We report a classical-decisive quantum internet architecture in which the integration of quantum information into advanced photonic technologies enables efficient entanglement distribution over a commercially deployed fiber network. On-chip precise synchronization between classical headers and quantum payloads enables dynamic routing and networking of high-fidelity entanglement guided by classical light. The quantum states are preserved through real-time error mitigation, relying solely on classical signal readout without disturbing quantum information. These classical-decisive features demonstrate a practical path to a scalable quantum internet using existing network infrastructure and operating systems.

A single-photon state was generated by heralding cavity-enhanced spontaneous parametric downconversion in a PPKTP optical parametric oscillator. The Wigner distribution was reconstructed by quantum state tomography, using photon-number-resolving measurements with a system efficiency of 58±2%. © 2019 The Author(s)

A cost-effective architecture for quantum cryptography has been demonstrated in which a single receiver positioned at a network-hub node is shared by many end users to exchange secret encryption keys. See Letter p.69 Quantum key distribution (QKD) is a process allowing secure information exchange between a transmitter and receiver with access to both classical and quantum resources. Its use has been limited to niche applications in dedicated high-security networks, not least because it becomes extremely resource-intensive when multiple users require access to the system. Here, Bernd Frohlich et al. outline the principles of a new QKD system, termed a 'quantum access network', based on simple and cost-effective optical telecommunication technologies. They then demonstrate the concept experimentally in a 64-user network in which, for simplicity and economy, all users share a single photon detector placed at a key node in the network. The authors suggest that this advance could lead to the adoption of quantum technologies as routine in the secure transmission of data.

We show that both the classical as well as the quantum definitions of the Fisher information faithfully identify resourceful quantum states in general quantum resource theories, in the sense that they can always distinguish between states with and without a given resource. This shows that all quantum resources confer an advantage in metrology, and establishes the Fisher information as a universal tool to probe the resourcefulness of quantum states. We provide bounds on the extent of this advantage, as well as a simple criterion to test whether different resources are useful for the estimation of unitarily encoded parameters. Finally, we extend the results to show that the Fisher information is also able to identify the dynamical resourcefulness of quantum operations.

In cryptography, oblivious transfer (OT) is an important multi-party cryptographic primitive and protocol, that is suitable for many upper-layer applications, such as secure computation, remote coin-flipping, electrical contract signing and exchanging secrets simultaneously. However, some no-go theorems have been established, indicating that one-out-of-two quantum oblivious transfer (QOT) protocols with unconditional security are impossible. Fortunately, some one-out-of-two QOT protocols using the concept of Crépeau’s reduction have been demonstrated not to conform to Lo’s no-go theorem, but these protocols require more quantum resources to generate classical keys using all-or-nothing QOT to construct one-out-of-two QOT. This paper proposes a novel and efficient one-out-of-two QOT which uses quantum resources directly instead of wasting unnecessary resources to generate classical keys. The proposed protocol is not covered by Lo’s no-go theorem, and it is able to check the sender’s loyalty and avoid the attack from the receiver. Moreover, the entangled state of the proposed protocol is reusable, so it can provide more services for the participants when necessary. Compared with other QOT protocols, the proposed protocol is more secure, efficient, and flexible, which not only can prevent external and internal attacks, but also reduce the required resources and resource distribution time.

We report the implementation of a high-rate source of single- and two-photon states. By combining the advantages of short pulses and cavities, heralding rates as high as 200 kHz have been obtained for the single photons, as well as 250 Hz for the two-photon states. In this setup, homodyne measurements are conditioned by the heralding of the quantum states thanks to the introduction of a low-loss optical delay line in the heralded states path. This enables the detection of most of the heralded events, and fidelities reaching 68.5% (91% with correction for detection efficiency) and 50.4% (85% with correction) were obtained for the single- and two-photon states, respectively. Such high rates and fidelities in the generation of elementary Fock states may open the path for the production of complex quantum states.