Periodic Reporting for period 1 - CerQUIT (Certifying Large-scale Quantum Information Technologies)
Berichtszeitraum: 2018-06-11 bis 2020-06-10
The past decade has seen a surge of interest in quantum technologies, which promise many transformative applications. Proposals for quantum internet infrastructure would enable unconditionally secure transmission and manipulation of information. Engineered quantum systems allow for the simulation of complicated states of quantum matter with potentially transformative impacts on quantum chemistry and drug design. In the longer term, a universal, fault-tolerant quantum computer would represent an entirely new frontier in high-performance computing with general applications for problems across science and industry. However, many of the most promising quantum technologies are currently hamstrung by the lack of rigorous methods for certifying their performance and quantifying the probability of failure. This task will be critical if the substantial investment in these technologies is to bear fruit, as transparent certification metrics and a framework for standards and specifications are essential for the widespread adoption and manufacture of any technology.
The widespread use of robust, scalable, and affordable quantum devices, should it come to pass, would represent nothing short of a technological and industrial revolution. In an information age, quantum cryptography offers a radically new approach to problems of data security. It is also now widely believed that Moore’s Law -the exponential scaling in processing power that has driven decades of economic and technical advancement- is coming to and end, while the problems of logistics, optimisation, data analysis which rely on high-performance computing no less compelling. Thus the future of quantum information technology, nascent as it may presently be, represents a radically different path towards solving these problems.
The main scientific objective of this proposal is the design of innovative and efficient tools for the certification of quantum states and processes, particularly infinite dimensional systems, and their application to QI protocols. A particular feature of many of the objectives is the adoption of what is called a “composable” certification framework which provides certificates (usually some failure probability) for individual devices or protocols that can be simply combined to calculate a certificate for some larger, composite protocol. Although valuable in all contexts, this framework is particularly crucial in a cryptographic setting and is in fact mandatory if the outputs of quantum cryptography protocols (e.g.secret keys) are to be used in real-world applications.These objectives would represent a significant advance the state-of-the-art in the theoretical understanding of quantum mechanical systems, and should pave the way for high-performance, rigorously certified QI technologies.
The widespread use of robust, scalable, and affordable quantum devices, should it come to pass, would represent nothing short of a technological and industrial revolution. In an information age, quantum cryptography offers a radically new approach to problems of data security. It is also now widely believed that Moore’s Law -the exponential scaling in processing power that has driven decades of economic and technical advancement- is coming to and end, while the problems of logistics, optimisation, data analysis which rely on high-performance computing no less compelling. Thus the future of quantum information technology, nascent as it may presently be, represents a radically different path towards solving these problems.
The main scientific objective of this proposal is the design of innovative and efficient tools for the certification of quantum states and processes, particularly infinite dimensional systems, and their application to QI protocols. A particular feature of many of the objectives is the adoption of what is called a “composable” certification framework which provides certificates (usually some failure probability) for individual devices or protocols that can be simply combined to calculate a certificate for some larger, composite protocol. Although valuable in all contexts, this framework is particularly crucial in a cryptographic setting and is in fact mandatory if the outputs of quantum cryptography protocols (e.g.secret keys) are to be used in real-world applications.These objectives would represent a significant advance the state-of-the-art in the theoretical understanding of quantum mechanical systems, and should pave the way for high-performance, rigorously certified QI technologies.
The action produced several results leading to 8 papers, 7 published with 1 under review (see technical report)
1) Rigorous security analysis for continuous-variable quantum key distribution (CVQKD) incorporating realistic constraints on the eavesdropper: i) finite-coherence quantum memory (PRA, 99, 052336 (2019)) ii) limited entanglement generation (PRR, 2, 013208, (2020)).
2) The first composable security analysis for CVQKD incorporating a post-selection step to distill private correlations (PRA 101, 052335 (2020)).
3) An explicit protocol for certifying quantum information preservation in symmetry-protected topological phases (PRR, 2, 013120, (2020)).
4) A rigorous proposal for an efficient optical measurement scheme to certify stationary opto-mechanical entanglement (PRR, 2, 033244, (2020)).
5) The first review paper surveying techniques for certification, verification and benchmarking of quantum devices (Nat. Rev. Phys., 2, 382 (2020)).
6) Design, analysis and implementation of an ultra-fast, real-time, source-device-independent quantum random number generator, generating composably secure randomness at over 8 Gb/s (accepted in PRX).
7) First finite-size composable analysis of CVQKD over free-space optical channels including techniques such as clusterisation and post-selection which substantially improve performance (under review at PRA).
8) First protocol for multipartite entanglement based secret sharing outperforming all bipartite protocols over bottleneck network topologies.
1) Rigorous security analysis for continuous-variable quantum key distribution (CVQKD) incorporating realistic constraints on the eavesdropper: i) finite-coherence quantum memory (PRA, 99, 052336 (2019)) ii) limited entanglement generation (PRR, 2, 013208, (2020)).
2) The first composable security analysis for CVQKD incorporating a post-selection step to distill private correlations (PRA 101, 052335 (2020)).
3) An explicit protocol for certifying quantum information preservation in symmetry-protected topological phases (PRR, 2, 013120, (2020)).
4) A rigorous proposal for an efficient optical measurement scheme to certify stationary opto-mechanical entanglement (PRR, 2, 033244, (2020)).
5) The first review paper surveying techniques for certification, verification and benchmarking of quantum devices (Nat. Rev. Phys., 2, 382 (2020)).
6) Design, analysis and implementation of an ultra-fast, real-time, source-device-independent quantum random number generator, generating composably secure randomness at over 8 Gb/s (accepted in PRX).
7) First finite-size composable analysis of CVQKD over free-space optical channels including techniques such as clusterisation and post-selection which substantially improve performance (under review at PRA).
8) First protocol for multipartite entanglement based secret sharing outperforming all bipartite protocols over bottleneck network topologies.
Several of the outcomes reported here represent substantial improvements in the state-of-the-art. These can be arranged in ascending order of practical feasibility with present day technology, and hence near term impact for applications and society in general.
Result 3) deals with the nascent field of symmetry-protected topological phases, which are still far from being readily observed and controlled in the laboratory. In fact, many basic features of these systems are only understood at a heuristic, intuitive level with a primary candidate being role of disorder (essentially small random perturbations to the dynamics) as a candidate to localise and hence better protect encoded quantum information. The result here represents arguably the most comprehensive quantitative analysis to date which broadly confirms this intuition while highlighting important variations in behaviour based upon the precise details of the encoding.
A more advanced, but still early-stage quantum information platform is opto-mechanics, where the combination of highly non-linear mechanical dynamics with fast, efficient optical technology offers an attractive future platform for metrology (particularly high-precision force sensing) and even full scale quantum computation. At this point however, it is still crucial to develop robust techniques for verifying the quantum properties of these systems and this work presents the a rigorous, practical protocol to verify stationary entanglement generation between optical and mechanical systems that only requires measurements. Our results show that this technique should be applicable in current experimental setups.
Results 1) and 2) an d 7) represent the cutting edge of CVQKD protocols containing a rigorous security proof and analysis of several techniques for increasing the performance of these schemes by adopting sophisticated data processing techniques and for the first time presenting a comprehensive framework for incorporating additional realistic physical constraints on potential eavesdroppers in a quantum network. These papers predict some of the highest rates ever reported for CVQKD schemes in the composable, finite-size framework that is crucial for real world applications. Finally, 7) presents the first composable finite-size analysis of a CVQKD protocol carried out over a free-space channel.
Finally, 8) presents probably the most dramatic result of this fellowship. Truly random numbers are an extremely valuable resource in many fields from cryptography to simulation. In this work we design and analyse an ultra-fast photonic QRNG that is completely independent of the light photons. This means that the photonic source can be completely unknown or even maliciously controlled. The generation rate of just over 8 Gb/s is more than 6 orders of magnitude faster than the previous source-independent result, and is the fastest composably secure QRNG ever reported. Moreover, the protocol uses only off-the-shelf devices, demonstrating that high performance QRNG’s are within reach of commercial implementation.
Result 3) deals with the nascent field of symmetry-protected topological phases, which are still far from being readily observed and controlled in the laboratory. In fact, many basic features of these systems are only understood at a heuristic, intuitive level with a primary candidate being role of disorder (essentially small random perturbations to the dynamics) as a candidate to localise and hence better protect encoded quantum information. The result here represents arguably the most comprehensive quantitative analysis to date which broadly confirms this intuition while highlighting important variations in behaviour based upon the precise details of the encoding.
A more advanced, but still early-stage quantum information platform is opto-mechanics, where the combination of highly non-linear mechanical dynamics with fast, efficient optical technology offers an attractive future platform for metrology (particularly high-precision force sensing) and even full scale quantum computation. At this point however, it is still crucial to develop robust techniques for verifying the quantum properties of these systems and this work presents the a rigorous, practical protocol to verify stationary entanglement generation between optical and mechanical systems that only requires measurements. Our results show that this technique should be applicable in current experimental setups.
Results 1) and 2) an d 7) represent the cutting edge of CVQKD protocols containing a rigorous security proof and analysis of several techniques for increasing the performance of these schemes by adopting sophisticated data processing techniques and for the first time presenting a comprehensive framework for incorporating additional realistic physical constraints on potential eavesdroppers in a quantum network. These papers predict some of the highest rates ever reported for CVQKD schemes in the composable, finite-size framework that is crucial for real world applications. Finally, 7) presents the first composable finite-size analysis of a CVQKD protocol carried out over a free-space channel.
Finally, 8) presents probably the most dramatic result of this fellowship. Truly random numbers are an extremely valuable resource in many fields from cryptography to simulation. In this work we design and analyse an ultra-fast photonic QRNG that is completely independent of the light photons. This means that the photonic source can be completely unknown or even maliciously controlled. The generation rate of just over 8 Gb/s is more than 6 orders of magnitude faster than the previous source-independent result, and is the fastest composably secure QRNG ever reported. Moreover, the protocol uses only off-the-shelf devices, demonstrating that high performance QRNG’s are within reach of commercial implementation.