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1-2 Oblivious Transfer is a cryptographic primitive in which a sender holds two bits, and a receiver receives one of them in such a way that the receiver does not learn both bits, and the sender does not know which of the bits the receiver has obtained. Perfect Quantum Oblivious Transfer is not possible, but it is possible to have protocols where cheating probabilities for the parties are bounded. Previous
research has found security bounds of 2=3 for general and 0:749 for symmetric pure quantum states. Here we examine a series of incomplete protocols, which means protocols with inherent probability for errors, that allow for security against the sender by no-signalling without allowing the receiver to cheat with unity success probability.
We characterise all incomplete protocols using symmetric states and compare dierent examples for implementable protocols with particular focus on the use of coherent states. Easiest to implement is a protocol in which classical bit value pairs are mapped to four phases +,-,+i,-i of a coherent state, which are distinguished using a single homodyne detection measurement. We show that using single photon BB84 like states provides better performance in terms of security than our coherent state protocols.

Quantum 2020

Imperfect quantum oblivious transfer where the sender cannot cheat

multi-party computation

security bound

oblivious transfer

quantum communication

cryptography

The Institute of Physics and IOP Publishing, in partnership with the Chinese Physical Society (CPS) and the University of Science and Technology of China (USTC) are proud to have brought together the international quantum science community online for this inaugural conference.


Early career and leading researchers from universities, industry and government worldwide came together to share, learn and collaborate on the latest research and emerging areas of high interest across quantum science and technology. The broad themes covered by Quantum 2020 included:

Quantum communication;
Quantum computing and quantum simulation;
Quantum sensing, metrology and imaging;
Quantum information theory, software and algorithms;
Quantum foundations;
Quantum technology in industry.
The four-day event featured talks from world-renowned scientists, interactive poster sessions and two exciting panel discussions on the themes of Quantum Technology in Industry and Quantum Technology Programmes Around the World.


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poster

Photon interference and bunching are widely studied quantum effects that have also been proposed for high-precision measurements. We construct and use a theoretical description of photon interferometry on rotating
platforms, specifically exploring the relation between noninertial motion, relativity, and quantum mechanics. We propose an experiment testing these relations where photon entanglement can be revealed or concealed solely by controlling the rotational motion of an interferometer.

Revealing and concealing entanglement with noninertial motion

The Google announcement of the first experimentally achieved result of the so-called quantum supremacy, based on exploiting the multiqubit entanglement to the problem of randomness verification [https://doi.org/10.1038/s41586-019-1666-5], attracted attention to the classically ungrasped nature of the randomness itself and its verification. The elusive infiniteness of true randomness correlating with the quantum entanglement of the infinite number of entangled qubits asks for a fundamental description. We proposed a simplistic theoretical concept linking the multiqubit entanglement with the randomness in the public patent application in 2017 [PCT/PL2017/000133-WO/2019/132679] and in Sci. Rep. in 2020 [https://doi.org/10.1038/s41598-019-56706-2], the latter coincided in time with Google team announcement. We show that on the theoretical level, the presented concepts are equivalent in the fundamental sense. We discuss our quantum multiqubit entanglement based protocol for quantum random number generation, with unique features, like secure public randomness testing, overcoming local computational restrictions, or arbitrarily diminishing of the average time of the complex randomness testing of finite length bit sequence at the cost of multi-qubit entanglement level. Here, the randomness of the generated single sequence proves the randomness of all the other simultaneously generated sequences (or the randomness of the shorter sequence proves the randomness of longer sequence), which is a crucial result based on the multiqubit quantum entanglement.

Multiqubit entanglement for public randomness testing vs Google's quantum supremacy

The initial research undertaken was aimed at examining the feasibility of adapting and implementing Topological Data Analysis (TDA) methods using Persistent Homology to meet requirements in the telecom domain. Persistent Homology based methods are especially useful in detecting anomalies in time series data and show good prospects of being useful in telecom network alarm data. Here, the special interest to this technique is a metric called the Wasserstein Distance, which shows how much two persistence diagrams correspondingly differ from one another. Calculating this metric is a minimum weight maximum matching problem on a bipartite graph. Existing classical methods of calculating the Wasserstein distance show polynomial time complexity O(n power 3).
We carried out a quantum study which involved converting this Wasserstein matching problem into a Quadratic Unconstrained Binary Optimization problem and minimizing it using a Quantum Annealer approach.
Our final focus on the TDA Wasserstein distance problem is the implementation of an alternate Combinatorial Optimization Quantum Algorithm which should theoretically be faster than existing classical methods, potentially yielding a quantum speedup in detecting anomalies in the future.

Quantum Topological Data Analysis for Anomaly Detection

The violation of seminal Bell-type inequalities in spin polarization correlation experiments stimulated speculations about quantum magic and nonlocality. Some authors claim that the quantum correlations are due to some instantaneous influences between distant quantum systems, that an individual quantum system may be at the same time here and a meter away or that the experimenters’ free will is an illusion. The narrative about the quantum magic is not only grounded in some failed attempts of providing more detailed description of quantum phenomena but also in the disturbing fact that there is no consensus about the interpretation of quantum theory. Nevertheless if one starts talking about magic this is the end of the science. Robert Griffith and several other authors came recently to the conclusion that the quantum nonlocality and the quantum steering are misleading notions which should be abandoned or renamed . The quantum correlations between the outcomes of real experiments with entangled physical systems are strong but imperfect and they can be explained in a locally causal way. it is not true that the entangled systems behave as pairs of fair dice showing always the same outcomes. The important message for quantum information community is that qubits are not the attributes of individual physical systems which can be changed instantaneously by the measurements performed on distant entangled partners.

Demystifying quantum nonlocality

The effect of photon-pair generation rate on quantum entanglement is analyzed.
Two techniques of producing polarization entanglement are compared: a continuously pumped spontaneous parametric down-conversion (SPDC) and a biexciton decay in a quantum dot. We made a comparison of the reconstructed entangled states in terms of performance under device-independent quantum key distribution. We found that the secure key rate of down-converted photon pairs is limited to 0.029 bits per detection window due to intrinsic multiphoton contributions. We also report that there exists one optimum gain for continuous-wave down-conversion sources. We find a bound for secure key rate extracted from SPDC sources and show that quantum dot sources can surpass them with future advancement of their capabilities.


Effect of source statistics on utilizing photon
entanglement in quantum key distribution

Long-lived quantum coherences detected in the Fenna-Matthews-Olson (FMO) light-harvesting complex have ignited the hunt for realistic models that can explain such dynamics. The extraordinary ~100% efficiencies presented by these complexes, operating under noisy environmental conditions, make them an important target for understanding and replicating their success in other practical applications. Despite the experimental developments, computer simulations are needed to perform a true approximation to understand the complex interactions that govern this system. Several methods have been explored to model this quantum phenomenon, mainly based on the quantum open systems theory. The evolution of approaches to the problem has gone from traditional methods which wouldn't consider the memory effects of the surroundings to more robust non-Markovian methods for the modelling of the system evolution with a better representation of environmental interactions. While quantum walks have proven to provide a mathematical framework for the study of energy transfer efficiency in the FMO complex, further characterization of operating conditions may lead to effective control and optimization of the system. We perform a parametric analysis about some physical features in the quantum regime involved during the quantum excitation process to get a comprehension about its non-trivial dependence on operation parameters. Thus, the analysis is conducted in terms of some relevant physical parameters in the system to track the complex global behavior in aspects as coherence, entanglement, decoherence times, transference times, and efficiency of the main process of energy capturing. As a complementary analysis from the derived outcomes, we compare those features for two different species as a suggestive possible roadmap to track genetic differences in the photosynthetic performance of the complex through its biological nature.

Quantum phenomena on life systems: a parametric deep view on the Fenna-Mathews-Olson complex

A variable behaving as a quantum in economic system is studied on the basis of quantum mechanics. The several formulas of relevant variable are derived along with this speculation. Thus a possible value for the common constant which may be understood as Planck constant in economic system is calculated. There, a concerned variable seems to exhibit a quantum behavior.
Recently it has been pointed out that there might be a similarity between the rational expectation hypothesis in economics and quantum mechanics, where their observers are both in respective systems. Nevertheless, on the other hand, the principle of uncertainty in economics has not yet been discovered so far. Therefore we will study on this problem by starting to formulate the basic equations respective which correspond to quantum mechanics. Here we pursue solely a behavior of certain representative variable with which an important econophysical quantity is newly introduced, and then discuss about Planck constant in economic system.


A variable behaving as a quantum in economic system

Relative quantum complexity is the measure of state distance between two quantum states. In quantum circuits, it could be argued as the number of fundamental quantum logic gates required to change the initial state of a quantum system to another state. From the Penrose diagrams of Ads/CFT black holes, it has been analyzed that the volume of black holes increases with time. The astounding similarity between the growth of quantum complexity and the volume of black holes is believed to be the fundamental postulate to quantize gravity. Here, we implement a simulation model to demonstrate the power of one clean qubit. We explicate how addition of one clean qubit could increase the uncomplexity of a maximally complex state. We explore the clean qubit computation in IBM quantum experience platform by designing the circuits and running them on IBM QASM simulator. This one clean qubit computation is realized for maximally complex five states made of single-, two-, three-, four-, and five-qubit systems and the results are discussed by comparing the power of one thermal photon on the accessible spacetime of an observer near the black hole horizon.

Simulation Model for complexity in Blackholes and demonstration of power of clean qubit using IBM QX

At present, the surface-electrode ion trap is an important device to realize large-scale and integrated quantum information processing. However, there are still a series of problems in the fabrication process of the surface-electrode ion trap, the biggest disadvantage is that the surface topography is difficult to control during the fabrication. The rougher the surface, the worse the electrical and trapping ability of the surface-electrode ion trap. Therefore, we propose a micro-nano technology to control topography of surface-electrode ion trap, which is suitable for the fabrication of most surface electrode ion traps. In addition, based on the proposed micro-nano technology of controlling surface topography, we give a method to fabricate surface electrode ion trap with specific surface roughness, and successfully fabricated surface electrode ion traps with roughness of 6.2 nm to 45 nm. Experiments have proved that the technology of controlling surface roughness is feasible and repeatable. By fabricating surface-electrode ion traps with different topogrphy, we may have a deeper understanding of the influence of surface roughness on the trap performance, especially in electrical performance, heating rate, ion trapping ability and other aspects.

Micro-nano technology for controlling the surface topography of thick film surface-electrode ion trap

A silicon wafer based platform consisting of quantum nano pillars is presented in terms of quantum sensing and imaging. The pillars can be fabricated on silicon wafers using plasma processing under chlorine atmosphere. The pillars so produced on silicon wafers are still crystalline and their surfaces can be smoothed under control. The density of the pillars is very high, that is ⁓1010 cm-2. They have a tapered like structure with tip ends of few atomic sizes, where quantum size effects are dominating optical properties, such as ultrafast radiative recombination down to femtosecond regime at blue spectral region, offering interesting applications of quantum information processing involving ultrafast optical switching. 
Quantum pillars form an interesting application platform for identifying of chemical and biological species. The ensemble of quantum pillars can accommodate related species for subsequent measurements using quantum qubit systems such as diamond NV centers. 


Imperfect quantum oblivious transfer where the sender cannot cheat

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