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American Journal of Engineering and Applied Sciences

Review Technology: Advances and Trends

1Lidong Wang and 2Cheryl Ann Alexander

1Institute for Systems Engineering Research, Mississippi State University, Vicksburg, Mississippi, USA 2Institute for IT innovation and Smart Health, Vicksburg, Mississippi, USA

Article history Abstract: Quantum science and have become Received: 30-03-2020 significant areas that have the potential to bring up revolutions in various Revised: 23-04-2020 branches or applications including aeronautics and astronautics, military Accepted: 13-05-2020 and defense, meteorology, brain science, healthcare, advanced

manufacturing, cybersecurity, artificial intelligence, etc. In this study, we Corresponding Author: Cheryl Ann Alexander present the advances and trends of quantum technology. Specifically, the Institute for IT innovation and advances and trends cover quantum computers and Quantum Processing Smart Health, Vicksburg, Units (QPUs), quantum computation and learning, Mississippi, USA , (QKD), quantum Email: [email protected] and quantum satellites, quantum measurement and quantum sensing, and post-quantum blockchain and quantum blockchain. Some challenges are also introduced.

Keywords: Quantum Computer, , Quantum Network, Quantum Key Distribution, , Quantum Satellite, Quantum Blockchain

Introduction information and the computation that is executed throughout a transaction (Humble, 2018). The Tokyo QKD metropolitan area network was There have been advances in developing quantum established in Japan in 2015 through intercontinental equipment, which has been indicated by the number of cooperation. A 650 km QKD network was established successful QKD demonstrations. However, many problems between Washington and Ohio in the USA in 2016; a still need to be fixed though achievements of QKD have plan of a 10000 km QKD backbone network was been showcased. Main features of QKD technology lie in: launched in the country. A quantum metropolitan area (1) Communication is generally fulfilled on a hop-by-hop network was estAablished in the UK in 2016 and a basis due to a main characteristic of the QKD network—no practical national network for QKD and an international available quantum router or quantum repeater in practice; QKD network was planned. The Phase I network with a (2) QKD links are at all times performed in a point-to-point total length of about 256 kilometers was established in manner, thus leading to a restricted distance and a key rate South Korea in 2016. The Beijing-Shanghai Trunk Line that is inversely proportional to the limited distance. of QKD was created in China in 2017 and applications in Furthermore, QKD links are possibly unavailable if the electric power, finance and government administration public channel is congested or there is not enough key were demonstrated (Liu et al., 2018). material (Shahid et al., 2020). The Personal Identifiable Information (PII) leak from Twin-field QKD was developed to obtain a remote big consumer databases, including social security numbers, key distribution with a maximum distance of secure financial status and additional private information have transmission. However, there were still some problems become a major concern and increased the interest in in the source part though the security of the twin-field reliable methods of sensitive information processing. A QKD was ensured in its detection part. The source of growing requirement of online applications in healthcare light had been regarded to be a very good and financial areas highlights worries about information though this assumption was not met in an actual QKD sharing and privacy. Quantum technology has the potential system, which led to secure problems in practice. A to handle the privacy worries or concerns using quantum protocol called Sending-or-Not-Sending (SNS) was put cryptographic methods such as super dense coding, forward for fixing the security problems. A condition quantum seals and QKD, which help protect information was discussed that the Number Distribution during the information transmission. Progress in quantum (PND) of the source is unknown for the SNS protocol. It computing has offered some techniques of obscuring stored was demonstrated a security analysis is still valid for a

© 2020 Lidong Wang and Cheryl Ann Alexander. This open access article is distributed under a Creative Commons Attribution (CC-BY) 3.0 license.

Lidong Wang and Cheryl Ann Alexander / American Journal of Engineering and Applied Sciences 2020, 13 (2): 254.264 DOI: 10.3844/ajeassp.2020.254.264 source with an unknown PND. It was shown that the connected quantum computer in a trapped ion system and SNS protocol performance in the light source monitoring has demonstrated algorithms with successful rates above the enables to keep nearly unchanged (Gao et al., 2019). Bounded-error Quantum Polynomial (BQP) threshold. The Standard has been thought to Hidden Shift (HS) and Bernstein-Vazirani (BV) algorithms govern all the processes of human consciousness such as have been compiled into native gates and executed on the emotions, personality, beliefs, psychology, thoughts, etc. hardware. The trapped ion quantum computer has been The brain-based consciousness has been considered as a used to accomplish the quantum implementation of the HS dynamic self-awareness concept, constructed by the and BV algorithms (Wright et al., 2019). brain’s cortical neurons as a field A framework for hybrid quantum-classical that continuously receives information/energy from the algorithms was presented that uses a quantum computer brain, evaluates and processes the information and (substantially smaller compared with the problem size). initiates responses. External sensory information that is Given a randomly small ratio of the quantum computer modelled as quantized electromagnetic waves has been to the problem size, a polynomial speedup for classical regarded to feed cortical neurons and ultimately build the divide-and-conquer algorithms was achieved. A trade-off brain-based consciousness Hamiltonian. Any external between the problem size and the speedup can be information or energy, instantly reaching to the brain- achieved. A small quantum computer can considerably based consciousness Hamiltonian, has been considered speed up the solving process of a small-size problem. as a perturbation (Erol, 2019). Also, it enables to obtain a more modest speedup of a The main purpose of this paper is to deal with the larger instance (Ge and Dunjko, 2020). advances and trends of quantum technology. Some A quantum computer can offer substantial speedup in challenges of quantum technology will also be presented. machine learning. Algorithms that require quantum speedup The following is the arrangement of the rest of the paper: in runtime rely on an efficient Quantum Random Access section 2 presents quantum computers and QPUs; Memory (QRAM) (a critical component) in addition to a section 3 introduces quantum computation and quantum quantum computer. In a QRAM, the number of required machine learning; section 4 describes quantum network; quantum routing operations scales up exponentially with the section 5 introduces QKD; section 6 presents of in the algorithms (Gao et al., 2018). teleportation and quantum satellites; section 7 describes Quantum memories are a cornerstone of quantum quantum measurement and quantum sensing; section 8 computers as well as a global-scale quantum Internet with deals with post-quantum blockchain and quantum high performances. Low retrieval efficiency is a main blockchain; and section 9 is the conclusion. problem of quantum memories. A High-Retrieval- Efficiency (HRE) was defined for a near- Quantum Computers and Quantum term quantum device. A unit of the HRE quantum memory Processing Units was integrated with local unitary operations on its hardware level and utilized cutting-edge technologies in quantum Superconductors, quantum dots, ion traps, linear machine learning. It was proven the local unitary of the optics, donor systems, distributed and monolithic HRE quantum memory achieves an optimized and diamonds and topological help to unsupervised readout procedure. It was shown that the develop quantum computers. The 4th-generation readout procedure of the HRE quantum memory was quantum computer utilizes the technology of topological accomplished without any information regarding an input quantum computing (also called anionic quantum quantum system or an unknown quantum operation of a computing) (Gyongyosi and Imre, 2019). Trapped quantum register. The retrieval efficiency of the HRE atomic ions provide one of primary physical platforms quantum memory and the output of the Signal-to-Noise for realizing a completely functional quantum computer, Ratio (SNR) was evaluated. The HRE quantum a programmable quantum computer prototype was memory is an especially convenient unit for a gate- displayed, and its performance was compared with that model quantum computer and the quantum Internet of a superconducting quantum computer with a similar (Gyongyosi and Imre, 2020). size. Among all of technologies, trapped ion qubits IBM launched the IBM Q Experience, which made demonstrate the highest gate quality. Despite promises, universal quantum computers accessible to the public further technical innovation is necessary to increase the through the cloud service. IBM Q Experience offers an number of qubits in a quantum computer module, online platform for experimental testing of quantum enhance logic gates quality, and realize scalable increase fundamentals and various applications in using multiple modules (Maslov et al., 2019). quantum . (developed by IBM) There have been several superconducting quantum provides tools for users who are required to run their computing platforms with a big qubit number such as quantum programs on prototype quantum simulators and IBM and Rigetti. A powerful programmable quantum devices. IBM has developed 20-qubit and 50-qubit computer has been constructed that is an 11-qubit fully quantum processors (Huang et al., 2020a).

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HPC QC them on quantum hardware utilizing a back-end connection to the cloud service of IBM Quantum Experience CPU QPU (Steiger et al., 2018). Industry interest has brough two major products: language Q# (Python-compatible) of Microsoft and Python package CPU QPU qiskit of IBM. Each of them provides a user with tools to compute or manipulate with the qubit logic that interfaces CPU QPU with classical programming. The code written with quantum algorithms can be executed (Keplinger, 2018).

Quantum technology, particularly quantum Fig. 1: An asymmetric multiprocessor model using a QC computing, has the potential to bring a great boost to server, for instance, a type of cloud-based QC Machine Learning (ML). Many conceptual connections exist between quantum computing and machine learning. How Quantum Processing Units (QPUs) integrate Some quantum algorithms can provide an exponential with a current or future High-Performance Computing speed increase for significant tasks. One algorithm called (HPC) system architecture was investigated through the HHL algorithm is the foundation of the existing considering the functional and physical design Quantum Machine Learning (QML) minirevolution. requirement. Integration pathways were examined that Many other quantum ML algorithms either extend HHL are differentiated by use cases expected for an HPC or use it as a subroutine. Additional intriguing algorithms, system and infrastructure constraints on QPUs. In a e.g., Quantum Support Vector Machines (QuSVMs) and loose integration path, QPUs are isolated operational quantum Principal Component Analysis (PCA) also have elements that need to interact with a host HPC system the potential of great speed-up. Furthermore, an algorithm through a network interface. This is an effective client- of quantum-inspired tensor-network for ML has been server model illustrated in Fig. 1 (Britt and Humble, proposed and begun to show intriguing merits. However, a 2017). The concept of Quantum Computing (QC) as a unified theory of quantum learning has not been developed service provides ease of use and more flexibility at the for quantum-enhanced ML (Sarma et al., 2019). price of communication latency. QML tasks such as quantum classification, boosting Quantum Computing (QC), quantum pattern recognition, Quantum Computation and Quantum adiabatic QC, and quantum process tomography and Machine Learning regression have been discussed. Quantum algorithms for A field that has been made remarkable progress is outlier detection, neighborhood graph, and smart quantum computation with different physical platforms initialization of cluster center have been developed. In among which superconducting quantum circuits and addition, the implementation of QuSVMs have been trapped ions are the most prospective. Various quantum presented (Nawaz et al., 2019). algorithms have been performed to show scaling issues, Quantum Fourier transform, quantum error- machine learning, the concepts of error correction, correction methods, quantum communication protocols, systems, many-body localization, the simulation of light- Quantum teleportation, and QKD play key roles in the matter systems, the modeling spectra of molecules and implementation of distributed quantum computation. other fermionic systems, etc., (Zhukov et al., 2019). Their realization is essential for the development of the There are two major approaches to achieving practical quantum Internet. The realization of some essential QC in the industry: (QA) and the gate protocols for quantum reinforcement learning (utilizing model (also called the circuit model). QA is a method of superconducting quantum circuits) was studied. employing the physics of quantum phase transitions to Superconducting quantum circuits help quantum conduct computation. A phase transition is a discrete information processing and quantum computation. A change in some macroscopic properties of a physical QuSVM for big data classification was defined. The system. A QPU of a D-Wave quantum computer has Support Vector Machine (SVM) can be executed on a completed the annealing process. Among all QC platforms quantum computer. A of association under development, Annealing-based QC provides the most rules mining and an issue of the quantum mixing of viable way forward for connecting quantum hardware to a Markov chains for unusual distributions were practical application (McGeoch et al., 2019). researched. The quantum Boltzmann machine was ProjectQ is an open source software framework of studied and a novel ML approach (based on the quantum QC. A high-level quantum language has been Boltzmann distribution) was presented. The possibility implemented as a domain-specific language embedded in of employing quantum annealing processors such as D- Python language. The framework permits quantum Wave to train a quantum Boltzmann machine was algorithms testing through simulations and enables to run analyzed. The data discovery driven by a quantum

256 Lidong Wang and Cheryl Ann Alexander / American Journal of Engineering and Applied Sciences 2020, 13 (2): 254.264 DOI: 10.3844/ajeassp.2020.254.264 annealer was studied in which a binary classifier uses a Searchable Encryption (SE) is an encouraging method quantum annealer to generate a reliable class estimator. for protecting users’ sensitive data in cloud computing A classical- quantum Deep Learning (DL) framework for while maintaining search capability on the server side. For industrial data sets for near-term devices was also example, it permits a server to search for encrypted data studied (Gyongyosi and Imre, 2019). without the leak of information in the plaintext data. A Full- Outspreading fundamental the concepts of Artificial Blind Quantum Computation (FBQC) model was Neural Networks (ANNs) and quantum information developed that is multi-client and universal circuit-based. processing, a Quantum Neural Networks (QNNs) Various clients with limited quantum ability outsourced the concept was introduced. Advantages of QSVMs and key generation to a trusted key center and uploaded their QNNs over classical SVMs and ANNs according to encrypted data to a data center. A quantum searchable reliability, scalability, processing speed, small scale and encryption scheme for the cloud data was then proposed fast learning motivates the exploration of these methods through combining Grover searching algorithm and the in fixing diverse problems in wireless communication multi-client FBQC model (Liu et al., 2019). networks. The progress in ML and QC methods has opened new horizons of fulfilling Deep QML methods Quantum Network such as Deep QNNs. Quantum-assisted Deep Learning (DL) has been attracting a great attention for improving A quantum network is composed of essential the performance metrics of communication networks. quantum hardware components including nodes, QC-based algorithms for DL are expected to influence quantum repeaters, and the . A node is a ML greatly (Nawaz et al., 2019). quantum processor connected to the quantum network. A Quantum speedup for reinforcement learning has a quantum repeater extends a short distance and permits great potential for an agent-environment paradigm. cubits to be arbitrarily transmitted over a large distance. Progress in quantum-enhanced reinforcement learning The quantum channel supports quantum has been presented. In the context of a communication transmission. It can be a fiber optic channel. The system, methods of quantum-inspired reinforcement development of quantum switch distribution device learning for optimal spectrum assignment have been technologies has been growing fast. A switch is a device studied (Nawaz et al., 2019). The advantage of quantum with a function of finding and transmitting data to the next reinforcement learning lies in a specific part of the receiver (Yaşar and Yilmaz, 2019). A quantum network algorithm which interacts with a classical environment, structure is shown in Fig. 2 (Wehner et al., 2018). produces results in a quantum environment and the A plug-and-play method that enables to synchronize process is reversible. The algorithm works in such a way building the blocks of a quantum network in an all- and forecasts the output in an optimal manner. The optical approach was implemented. It relied on robust processing and learning of the machine should be classical telecommunication and nonlinear optical executed in parallel for a high implementation efficiency technology and could be performed in a general way of the algorithm (Gupta et al., 2017). with off-the-shelf components It was enabled to achieve The security of ML has become a significant issue. a synchronization that is of high quality and compatible Classical ML algorithms, e.g., SVMs, clustering, with a high network-operation rate. It was tested through synchronizing two distant photon pair sources. It paved a Principal Component Analysis (PCA) are vulnerable to way to the synchronization of long-distance quantum the changes of features, input data, and ultimate model networks based on a fiber, free-space, and hybrid parameters or hyper-parameters that are already learned. solution. In addition, the synchronization approach Attackers can have various purposes, e.g., an increase in permitted to add as many nodes (such as quantum false positive rate or false negative rate. The study of memories and sources) to a quantum network as subverting an ML system by motivated attackers has necessary. It could be regarded as a useful method of been defined as adversarial ML. In adversarial quantum scaling up quantum networks (D’Auria et al., 2020). ML, some ways were discussed in which quantum Software Defined Networking (SDN) principles have information could be utilized for making quantum been used to create a converged classical-quantum classifiers private as well as secure. A type of quantum network that shares the logical and physical PCA was demonstrated. It was shown that a quantum infrastructure among classical and quantum channels. A quantum enabled SDN structure has been proposed. It method could be employed to implement a private form united under the same management as the classical and of clustering with k-means. A quantum approach was quantum communications, making network optimization introduced for boosting and bagging that used quantum better utilize all kinds of resources compared with a superposition over classifiers or splits of a training typical quantum network structure in which an ad hoc dataset to aggregate many more models than classical network is used to run in parallel to a usual one for qubit methods (Wiebe and Kumar, 2018). transmission (Aguado et al., 2019).

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Quantum End node channel

Quantum Switch repeater

Fig. 2: A quantum network structure

The security of quantum communication over a Inspired by the substantial similarity between mobile network with the existence of a malicious adversary who ad-hoc networks and the QKD technology, researchers eavesdrops and contaminates states was studied. The proposed a model of the Quality of Service (QoS) that network is composed of noiseless quantum channels includes metrics for deciding the states of quantum and together with the unit capacity and nodes that apply public channels as well as the overall state of QKD links. noiseless quantum operations. An asymptotically secret They also proposed a routing protocol to minimize the as well as correctable quantum network code was consumption of cryptographic keys and obtain high-level presented as the quantum extension of classical network scalability (Shahid et al., 2020). codes. The code was universal and structured without In principle, QKD provides unconditional security any knowledge of the topology of the network and through creating secret keys at a distance. For a specialized node operations. The quantum network code standard QKD, two spatially separated parties (we was executed through attaching a known communication often call them Alice and Bob) trust functions of their protocol of a secure classical network. It could be devices. However, this is a very strong assumption. A regarded as the generalization of quantum secret sharing protocol is called one-Sided-Device-Independent (Song and Hayashi, 2019). (SDI) QKD if one of devices is not trusted; it is called Device-Independent (DI) QKD when both the devices Quantum Key Distribution are not trusted. The three QKD scenarios are in correspondence with the hierarchy of quantum In , QKD is very noticeable. It correlations. The standard QKD requires that both is a technology of the physical layer and the technology Alice and Bob share entanglement or be connected by is immune to classical and quantum computational a channel that enables to keep entanglement. For SDI attacks or threats. It may be mathematically proven to be QKD, Alice and Bob are required to produce a secret secure and independent of the resources of adversaries key, which makes their systems violate a steering (Aguado et al., 2019). It is a technology for sharing inequality. In DI-QKD, the systems of the two parties encryption keys between two adjacent nodes. Because it (Alice and Bob) violate a Bell inequality. Intrinsic non- enables to identify any eavesdropping based on the locality and quantum intrinsic non-locality has been quantum theory, users can communicate securely while introduced as quantifiers for Bell non-locality. It has utilizing shared random numbers as encryption keys. A been proven they satisfy some desired properties, e.g., key management method was proposed for a QKD convexity, faithfulness, and monotonicity under shared network with a high speed. The design, execution, and randomness and local operations. Upper bounds on assessment of a key management method was presented secret-key rates have been established that are attainable (Takahashi et al., 2019). with SDI-QKD and DI-QKD. It has also been proven

258 Lidong Wang and Cheryl Ann Alexander / American Journal of Engineering and Applied Sciences 2020, 13 (2): 254.264 DOI: 10.3844/ajeassp.2020.254.264 that restricted intrinsic steerability is an upper bound on provided that was composed of networking secret-key rates in protocols of one-SDI secret-key- teleportation protocols and criteria to identify faithful agreement (Bennet and Daryanoosh, 2019). teleportation for general quantum computers with Quantum scissors were investigated as candidates modular structures and improve the reliability of for non-deterministic amplifiers in Continuous- quantum information processing (Huang et al., 2020b). Variable (CV) QKD. Such devices rely on single- Micius is a quantum experiment science satellite photon sources for their operations. The rate of secret designed to conduct quantum experiment at the scale of key generation for a protocol that used quantum space. One of objectives was to perform ground-satellite scissors was bounded based on exact analytical quantum teleportation that was of a main interest. This kind modeling for system components. Such a protocol can of teleportation was the first application of spaceborne and reach a longer distance than the counterpart with no low-noise Single-Photon Detectors (SPDs), received uplink amplification for certain non-zero values of excess configurations and placed a complex multiphoton setup on noise, which sheds light into the prospect of the ground (Yang et al., 2019). employing quantum scissors as an ingredient in CV A high-fidelity transmission of polarization with quantum repeaters (Azhar et al., 2019). encoded qubits plays a critical role in the quantum Some researchers have focused on realizing more communication of a long distance. The polarization efficient and practical QKD systems. An urgent problem encoding of has been the first choice for the is a requirement for easy and efficient realization of quantum communication with a long distance and over a reconciliation schemes for real-world QKD systems. free space, including satellite-based quantum Based on Low-Density Parity-Check (LDPC) codes, entanglement distribution. Transmission antennas with rate-adaptive schemes can accomplish an attractive polarization maintenance were designed and a execution of a key reconciliation process because they polarization compensation scheme used for satellite cover a full range of the channel parameter space with a was presented. In addition, entangled photons limited set of pre-defined mother codes. Some rate- were distributed from the ground to a satellite. This adaptive reconciliation schemes (based on the LDPC research has provided support for other work, for codes) were investigated, illustrating how their example, ground-to-satellite teleportation and the testing performance was compared with other set-ups in which of the model of gravitationally induced quantum fixed-rate non-adaptive LDPC codes (optimized for decoherence (Han et al., 2020). various channel conditions) were used. Especially, the Creating a global quantum communication network impact of rate-adaptive codes on decoding complexity depends on the integration of fiber-based networks and and subsequently overall secure key throughput was satellite-based links. A universal and basic model was quantified by simulations of an entanglement-based provided for the modelling and simulation of the loss version of a QKD protocol within the context of the resulted from a satellite-based optical link. It has entanglement source onboard a satellite (Ai et al., 2018). confirmed by simulations that quantum communication over a long distance could be realized not only Quantum Teleportation and Quantum employing medium-sized satellites (such as Micius of Satellites China), but also employing nano-satellites that permit to save costs of a global space-based quantum network Quantum teleportation offers a method of substantially. A performance analysis of various QKD transporting unknown quantum states between remote realizations was conducted, covering finite-key effects systems based on shared and (with a focus on various interesting application quantum measurement; therefore, it establishes an scenarios) (Liorni et al., 2019). essential element in making large-scale quantum QKD on satellite networks enables to overcome processors with a modular quantum structure and shortcomings of terrestrial optical networks, e.g., fulfilling various quantum information processing and difficulty of intercontinental domain communication and quantum computation tasks over the quantum attenuation over a fiber channel with a long distance. A network. Two protocols were proposed to teleport single satellite cannot fulfil QKD at ground stations on a qubits over an N-node quantum network in a chain- full day using existing schemes. In addition, research is a type or highly entangled box-cluster challenge due to the limitation of the satellite coverage state. The protocols were applicable to any size of such as the limited cover time of Low Earth Orbit modules and systematically scalable to any finite (LEO) satellites and high channel losses of number N. The protocol that was based on a box- Geostationary Earth Orbit (GEO) satellites. An cluster state was employed on a 14-qubit quantum architecture of trusted-repeater-based double-layer computer of IBM and N was up to 12. A toolbox was Quantum Satellite Networks (QSNs) that consist of

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LEO and GEO satellites was proposed to overcome However, little progress happened in improving the the limitations. The problem regarding Routing and understanding of joint measurements (Gisin, 2019). Key Allocation (RKA) for key-relay services over In the quantum communication where states are sent QSNs was addressed (Huang et al., 2020b). via a noisy channel, an optimal measurement can Using Terahertz (THz) frequencies was explored as identify which state has been sent via the channel though an approach to realizing quantum communication within the state may not be fully secured. A scheme of a constellation of micro-satellites in LEO. Quantum preserving an optimal measurement over a channel has communication between high-altitude terrestrial stations been called “channel coding of a quantum and the micro-satellite constellation was investigated measurement”. Approaches to preserving states have too. It was demonstrated that THz QKD and THz been called “channel coding of states”. A framework of quantum entanglement distribution are viable preserving a measurement on quantum systems deployment options for micro-satellites. There is a interacting with an environment was formulated and possibility for a simple integration of global quantum presented. Channel coding of qubit measurement was and wireless networks. Such an integration has been presented. It was shown that the measurement can be regarded as a significant step for global quantum preserved for any channel for both pairs of qubit states communication in the future. The possibility of and ensembles of equally possible states. The protocol employing THz frequencies for quantum radar that preserves a quantum measurement was applications in the LEO deployment context was demonstrated with quantum computers of IBM (Kechrimparis et al., 2020). discussed. Quantum radars show how entangled The quantum measurement incompatibility is a quantum states bring up better detection of remote typical feature in quantum . The existence objects via reflection (Wang et al., 2019). of incompatible measurements also means the no- SPDs play a significant role in a highly sensitive cloning theory. The measurement incompatibility was detection application, e.g., quantum communication, classified for a given set of measurements and a deep space optical communication and remote sensing hierarchy of quantum measurement incompatibilities and ranging. But adverse conditions in the space, e.g., was presented. The transition between various kinds increased radiation flux and thermal vacuum harshly of incompatible measurements was studied utilizing restrict their noise performances, lifetime, and the semidefinite program. A criterion for judging the reliability. An example of spaceborne SPDs with high incompatibility of a given multiple measurement was reliability and low noise was presented. The SPDs presented. Examples regarding unbiased qubit helped to establish a practicable satellite-based up- measurements were given in details. The link quantum communication that was validated on incompatibility of quantum measurements is a very useful the platform of a quantum experiment science tool in quantum information theory (Sun et al., 2020). satellite. The SPDs also offered a choice for weak Measurement-based Quantum Correlations optical signal reception in the space applications, e.g., (MbQCs) depend on how strongly an observer time transfer, deep-space optical communication, and perturbs an unobserved system. This differentiates satellite-based quantum application (Yang et al., 2019). MbQCs from traditional quantum correlations such as entanglement and discord though entanglement and Quantum Measurement and Quantum discord have been regarded as essential in quantum Sensing state discrimination and quantum computation tasks. MbQCs were used to clarify quantum information In quantum teleportation, quantum entanglement processing capabilities in quantum computation and has been exploited twice. First, entanglement is a discrimination. It was shown that “quantum teleportation channel” (entanglement MbQCs exist more generally than entanglement and between various systems in a distance). Second, entanglement is in the eigenvectors of a joint discord in optimal assisted quantum state measurement. Entanglement facilitates entirely new discrimination and deterministic quantum types of quantum measurement. After the discovery of computation with a single qubit. An MbQC-based quantum teleportation, there have been many dimension witness was proposed and analyzed in advances on , Bell-locality and more various noisy and noiseless scenarios. MbQCs were general quantum information theory. Similarly, great recently discovered to be relatively more resourceful progress has taken place in experimental than quantum entanglement and super quantum investigation, applied engineering, and even the discord in the field of mixed state industrial development of quantum technology. (Khalid et al., 2020).

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Quantum sensing (Q-sensing) utilizes nonclassical digital-signature schemes for a blockchain (Fernández- resources to enhance measurement precision. There have Caramès and Fraga-Lamas, 2020). been many applications such as bio-sensing, quantum Random sequences were generated as a tool to protect illumination, atomic clocks, quantum reading, and the transactions completely based on Bitcoins under an laser interferometer gravitational-wave observatory. assumption that the transition probability in quantum Entanglement can be extremely beneficial when a mechanics was observed as a full blockchain operation. An sensing task involves multiple parties. In principle, algorithm with integer-order Bessel functions was tested. A Continuous-Variable (CV) error correction codes can be formalism based on was presented that employed to improve the reliability of a protocol that permitted the simulation of the dynamics of blockchain for utilizes CV quantum information. Distributed quantum an e-commerce transaction (Nieto-Chaupis, 2019). sensing that is improved by CV error correction was QKD is a well-known method of quantum cryptography. The transparency and immunity of a studied (Zhuang et al., 2020). blockchain-based crypto-currency system was Quantum systems can be developed in the investigated through the simulation of a six-state QKD superposition of states and this particularity results in protocol. The generation of key rate was observed to phenomena called quantum entanglement and . guarantee a path for producing a better crypto-currency Q-sensing exploits both the properties to implement system (Azhar et al., 2019). enhanced sensors and measuring protocols. How to Safeguard measures were proposed through creating exploit the quantum features of molecular spins for Q- a framework of a quantum-secured and permissioned sensing was studied. Further particularity of molecular blockchain that is named Logicontract (LC). LC uses a spins may be exploited for Q-sensing at the nanometer digital signature scheme based on a QKD mechanism scale (Troiani et al., 2019). and a vote-based consensus algorithm to get consensus on a blockchain. Main deliverables were developed, Post-Quantum Blockchain and Quantum including a logic-based scripting language for writing Blockchain smart contracts on LC, a scalable consensus protocol used by LC, an unconditionally secure signature scheme The vulnerabilities of modern blockchain networks for LC that makes it immune to quantum computing and some potential post-quantum mitigation methods attacks and a quantum-resistant lottery protocol that were introduced. A lattice-based signature scheme was shows the utilization and power of LC (Sun et al., 2019). presented that can be used for securing blockchain Compared with conventional voting methods, e- networks over existing classical channels. Moreover, a voting has been used in various decision scenarios due to description of the Post-Quantum Blockchain (PQB) its convenience and low costs. An e-voting protocol with transaction was given in details. PQB is a quantum transparency in the voting process was proposed based information vision system. It is a classical blockchain on blockchain. It also enables to audit voters with system equipped with the post-quantum cryptography or incorrect operations and fight quantum attacks using the a storage structure of the classical blockchain with certificateless and code-based cryptography. quantum communication (Li et al., 2018). Specifically, the code based Niederreiter algorithm was The influence of quantum-computing attacks on a used to fight quantum attacks (Gao et al., 2019). blockchain was analyzed and how to employ a post- A smart contract based on light-weighted quantum quantum cryptosystem to mitigate such attacks was blind signature was proposed to boost the security studied. The most relevant post-quantum schemes were performance of blockchain smart contracts against investigated and their applications to blockchains were quantum attacks. The structure of the smart contract was studied. In addition, extensive comparison was presented built by five main lays that is shown in Table 1 (Cai et al., regarding the performance and characteristics of the 2019) and enables to deal with both quantum most promising post-quantum public-key encryption and information and classic information.

Table 1: The structure of a smart contract of blockchain based on the quantum blind signature User Layer Data Layer Management Layer Verification Layer Execution Layer Authority management Data collection Contract management Code generation Virtual machine Account management Data cleansing Protocol management Formal description Container Security verification Data processing Parameter management Formal verification Application interface Reputation management Data storage Business management Conformance testing Business application User's quantum blind Quantum information Quantum key Quantum signature Quantum state signature processing management verification restoration

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