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Quantum computation offers unique properties that cannot be paralleled by conventional computers. In particular, reading qubits may change their state and thus signal the presence of an intruder. This paper develops a proof-of-concept for a quantum honeypot that allows the detection of intruders on reading. The idea is to place quantum sentinels within all resources offered within the honeypot. Additional to classical honeypots, honeypots with quantum sentinels can trace the reading activity of the intruder within any resource. Sentinels can be set to be either visible and accessible to the intruder or hidden and unknown to intruders. Catching the intruder using quantum sentinels has a low theoretical probability per sentinel, but the probability can be increased arbitrarily higher by adding more sentinels. The main contributions of this paper are that the monitoring of the intruder can be carried out at the level of the information unit, such as the bit, and quantum monitoring activity is fully hidden from the intruder. Practical experiments, as performed in this research, show that the error rate of quantum computers has to be considerably reduced before implementations of this concept are feasible. [ABSTRACT FROM AUTHOR]

Grover's unstructured quantum search algorithm gives a quadratic speedup over classical linear search, provided that multiple accesses to the oracle are possible. In this paper, we show that in dealing with NP-complete decision-version problems, the quantum computing paradigm still outperforms classical computation, even if only one invocation of the oracle is allowed. The superiority of the quantum approach under such a restrictive condition can often be maintained even if a simple measurement strategy is chosen. A quantum decider utilizing only Hadamard gates and measurements in the computational basis has a better chance of discriminating between a problem with solution(s) and one without, when compared to the best separation achieved by a classical decider. In addition, the simple quantum measurement strategy is remarkably close to the optimal discriminating measurement, which itself is considerably more complex to devise and implement. If we further require the decider to be unambiguous (any definitive answer must be error-free), then a general positive operator-valued measurement can be devised to classify a problem as unsolvable, with some probability, after one consultation of the oracle. Such a feature remains impossible for a classical decider, even after any less than exhaustive oracle invocations. The inherent probabilistic nature of quantum mechanics seems to be at the heart of the advantage quantum computing exhibits over classical computation, in the context of deciding NP-complete problems based on a single oracle query. [ABSTRACT FROM AUTHOR]

This paper proposes a perimeter detection scheme based on the quantum physical properties of photons. Existing perimeter intrusion detection schemes, if using light, rely on the classical properties of light only. Our quantum sensor network uses the quantum property of spatial superposition of photons, meaning that a photon can simultaneously follow two different paths after going through a beam splitter. Using multiple Mach–Zehnder interferometers, an entire web of paths can be generated, such that one single photon occupies them all. If an intruder violates this web in some arbitrary point, the entire photon superposition is destroyed, the photon does not self-interfere any more and this event is detected by measurements. For one single photon, the intruder detection probability is limited theoretically but can be increased arbitrarily with the usage of a sequence of photons. We show both theoretical bounds as well as practical results of the proposed schemes. The practical results are obtained by simulation experiments on IBM Quantum platforms. The benefits of our quantum approach are: low power, invisibility to potential intruders, scalability and easy practical implementation. [ABSTRACT FROM AUTHOR]

Moving at the speed of light, the photon is the ideal physical support to transmit information. Polarization of a photon is the predominant quantum property used to encode information, but other encoding domains, such as the spatial-mode degree of freedom, have been considered. In this paper, we put forward the entanglement degree of freedom of a photon as an exploitable resource for encoding information in quantum cryptographic protocols. We show how classical information can be extracted from the quantum state of a photon by distinguishing between a singular, independent state and an entangled state through interferometry. We also give a direct application of our technique to quantum key distribution as a proof of concept for future quantum protocols that may use coding in the entanglement domain in combination with other degrees of freedom that are currently exploited for cryptographic purposes. [ABSTRACT FROM AUTHOR]

This paper proposes a different approach to pinpoint the causes for which an unconditionally secure quantum bit commitment protocol cannot be realized, beyond the technical details on which the proof of Mayers' no-go theoremis constructed. We have adopted the tools of quantum entropy analysis to investigate the conditions under which the security properties of quantum bit commitment can be circumvented. Our study has revealed that cheating the binding property requires the quantum system acting as the safe to harbor the same amount of uncertainty with respect to both observers (Alice and Bob) as well as the use of entanglement. Our analysis also suggests that the ability to cheat one of the two fundamental properties of bit commitment by any of the two participants depends on how much information is leaked from one side of the system to the other and how much remains hidden from the other participant. [ABSTRACT FROM AUTHOR]

Squiggle data is the numerical output of DNA and RNA sequencing by the Nanopore next generation sequencing platform. Nanopore sequencing offers expanded applications compared to previous sequencing techniques but produces a large amount of data in the form of current measurements over time. The analysis of these segments of current measurements require more complex and computationally intensive algorithms than previous sequencing technologies. The purpose of this study is to investigate in principle the potential of using quantum computers to speed up Nanopore data analysis. Quantum circuits are designed to extract major features of squiggle current measurements. The circuits are analyzed theoretically in terms of size and performance. Practical experiments on IBM QX show the limitations of the state of the art quantum computer to tackle real life squiggle data problems. Nevertheless, pre-processing of the squiggle data using the inverse wavelet transform, as experimented and analyzed in this paper as well, reduces the dimensionality of the problem in order to fit a reasonable size quantum computer in the hopefully near future. [ABSTRACT FROM AUTHOR]

Together with bit commitment, Oblivious Transfer is a very useful cryptographic primitive with important applications, most notably in secure multiparty computations. It has been long known that secure Quantum Oblivious Transfer can be achieved from a secure implementation of Quantum Bit Commitment. Unfortunately, it is also well known that unconditionally secure Quantum Bit Commitment is impossible, so building a secure Oblivious Transfer protocol on top of Quantum Bit Commitment is ruled out. In this paper, we propose a relatively simple quantum protocol for Oblivious Transfer which does not require qubit storage, does not rely on bit commitment as a primitive and is easily implementable with current technology, if the two actors are honest. The protocol is proven to be secure against any individual measurements and entanglement-based attacks. Any cheating attempt trying to speculate collective measurements would be considerably difficult to put in practice, even in the near future. Furthermore, the number of qubits used in our scheme (embodied as photons in a physical realization of the protocol) acts as a security parameter, making it increasingly hard to cheat. [ABSTRACT FROM AUTHOR]

Current quantum cryptographic protocols aim to distribute a classical secret key to be used afterwards in classical encryption/decryption schemes. We show in this paper that quantum information processing can be used to do much more than just key distribution. Simple quantum transformations augmented with the ability to store qubits in a quantum memory are the building blocks of a class of protocols allowing two parties to communicate secretly by encoding/decoding the exchanged message directly through quantum means, without the need to establish a secret encryption/decryption key first. Consequently, our quantum mechanical process of securely transmitting a message through a public channel is conceptually simpler than the two-step scenario with a quantum distributed classical key. In addition, since the encrypted message is only transmitted through a quantum channel, copying and off-line analysis of the transmission is impossible. Our algorithms rely on the common assumption that public information can be authenticated. In terms of security, the protocol using three encoding bases achieves the maximum detection rate of 33 % per qubit tested. The probability of catching a potential eavesdropper can be brought as close to 1 as desired by increasing the length of the signature string attached to the message. [ABSTRACT FROM AUTHOR]

Security in sensor networks, though an important issue for widely available wireless networks, has been studied less extensively than other properties of these networks, such as, for example, their reliability. The few security schemes proposed so far are based on classical cryptography. In contrast, the present paper develops a new security solution, based on quantum cryptography. The scheme developed here comes with the advantages quantum cryptography has over classical cryptography, namely, effectively unbreakable keys and therefore effectively unconditionally secure messages. Our security system ensures privacy of the measured data field in the presence of an intruder who listens to messages broadcast in the field. [ABSTRACT FROM AUTHOR]

Rank-varying computational complexity describes those computations in which the complexity of executing each step is not a constant, but evolves throughout the computation as a function of the order of execution of each step [2]. This paper identifies practical instances of this computational paradigm in the procedures for computing the quantum Fourier transform and its inverse. It is shown herein that under the constraints imposed by quantum decoherence, only a parallel approach can guarantee a reliable solution or, alternatively, improve scalability. [ABSTRACT FROM AUTHOR]

We develop an entanglement verification method not based on Bell inequalities, that achieves a higher reliability per number of qubits tested than existing procedures of this kind. Used in a quantum cryptographic context, the method gives rise to a new protocol for distributing classical keys through insecure quantum channels. The cost of quantum and classical communication is significantly reduced in the new protocol, while its security is increased with respect to other entanglement-based protocols exchanging the same number of qubits. To achieve this performance, our scheme relies on a simple quantum circuit and the ability to store qubits. [ABSTRACT FROM AUTHOR]

It has been said that quantum cryptography in general offers a secure solution to the problem of key enhancement. This means that two parties who already share a small secret key, can use quantum protocols to establish a new large secret key. This large secret key can be arbitrarily long and is unbreakable. Thus, to date, the main contribution of quantum cryptography has been believed to be quantum key enhancement. This paper shows that quantum cryptography can do significantly more. The quantum protocol described here distributes an unbreakable secret key to the two parties by relying on public information only. This is the first time that quantum cryptography is shown to be able to produce secret information using only public information. This contribution is also unique for cryptography in general, classical and quantum. [ABSTRACT FROM AUTHOR]

Determining the optimal location of a switching center in a tree network of users is accurately modeled by the median problem. A real-time approach is used in this paper to investigate the dynamics of such a communication network in two cases: (1) a growing tree of nodes associated with equal demand rates, and (2) a stream of corrections that arbitrarily change the demand rates at the nodes. The worst-case analysis performed in both situations clearly demonstrates the importance of parallelism in such real-time paradigms. It is shown that the error generated by the best sequential algorithm in the first case can be arbitrarily large. A synergistic behavior is revealed when the quality-up is investigated in the second case. [ABSTRACT FROM AUTHOR]

This paper is structured around the idea that a finite Universal Computer cannot be realized and presents in detail a series of unconventional computing paradigms supporting this idea from a quantum mechanical perspective. [ABSTRACT FROM AUTHOR]

The quantum model of computation not only offers entirely new ways to manipulate information, but also allows information processing tasks to be formulated in unconventional, genuine quantum mechanical terms. We show that the task of distinguishing among entangled quantum states combines entanglement and non-determinism in a way that makes the quantum solution impossible to simulate on any classical machine (even one equipped with the same measurement capabilities as the quantum computational device). A new class of information processing tasks is thus uncovered whose members are readily carried out by a quantum computer, yet are impossible to perform on any classical machine (whether deterministic or probabilistic). In the broad, unconventional context created by quantum mechanics, the computational power of a quantum computer is therefore strictly greater than that of a classical computer. [ABSTRACT FROM AUTHOR]

Abstract: The nearest-neighbor method can successfully be applied to correct possible errors induced into bit strings transmitted over noisy communication channels or to classify samples into a predefined set of categories. These two applications are investigated under real-time constraints, when the deadlines imposed can dramatically alter the quality of the solution unless a parallel model of computation (in these cases, a linear array of processors) is used. We also study a class of real-time computations, referred to as reactive real-time systems, that are particularly sensitive to the first time constraint imposed. [Copyright &y& Elsevier]

The paper is intended to be a survey of all the important aspects and results that have shaped the field of quantum computation and quantum information. The reader is first familiarized with those features and principles of quantum mechanics providing a more efficient and secure information processing. Their applications to the general theory of information, cryptography, algorithms, computational complexity and error-correction are then discussed. Prospects for building a practical quantum computer are also analyzed. [ABSTRACT FROM AUTHOR]

The authors reflect on the selected researched materials from the workshop on Unconventional Computational Problems held on August 13, 2007 in Kingston, Ontario. The authors briefly state that unconventional computation is committed to discovering new computing ideas that can solve problems that are difficult for ordinary computers. The authors add that the discussions from the researched materials will provide the reader insights about the theory of computing.

This paper studies the effect of quantum computers on Bitcoin mining. The shift in computational paradigm towards quantum computation allows the entire search space of the golden nonce to be queried at once by exploiting quantum superpositions and entanglement. Using Grover's algorithm, a solution can be extracted in time O ( 2 256 / t) , where t is the target value for the nonce. This is better using a square root over the classical search algorithm that requires O (2 256 / t) tries. If sufficiently large quantum computers are available for the public, mining activity in the classical sense becomes obsolete, as quantum computers always win. Without considering quantum noise, the size of the quantum computer needs to be ≈ 10 4 qubits. [ABSTRACT FROM AUTHOR]

Quantum bit commitment (QBC) is a quantum version of the classical bit commitment security primitive. As other quantum security primitives and protocols, QBC improves on cheating detection over its classical counterpart. The implementation of the QBC protocol below relies on the use of common quantum gates: the Hadamard gate used for orthonormal bases and the CNOT gate used to swap qubits. The protocol was run and tested on IBM quantum experience (IBM QX). IBM QX offers two different quantum environments: as a simulator and as a real quantum machine. In our implementation, honest and dishonest participants were considered. Results of both the simulation and the quantum execution were compared against the theoretical expectations. The IBM QX simulator gives results that match the theoretical model. The IBM QX real computer deviates from the expected behavior by a measurable amount. Using the standard deviation and the Hamming distance, the conclusion is that the quantum computer is usable as the difference to the simulator is within an acceptable margin of error. The QBC protocol of choice is fully secure against cheating by Bob. The only way Alice can cheat is using multi-dimensional entanglement. The cost for Alice to cheat is exponential in the number of qubits used, namely O (2 6 n + 3 k + 1) . [ABSTRACT FROM AUTHOR]