Quantum metrology promises improved sensitivity in parameter estimation over classical procedures. However, there is a debate the question of how scales with resources and number queries that are used Here, we reconcile physical definition relevant information-theoretical scaling terms query complexity quantum network. This leads to completely general optimality proof Heisenberg limit for metrology. We give an example our resolves paradoxes suggest sensitivities beyond limit, show...

Quantum computation represents a threat to many cryptographic protocols in operation today. It has been estimated that by 2035, there will exist quantum computer capable of breaking the vital scheme RSA2048. Blockchain technologies rely on for their essential sub-routines. Some these protocols, but not all, are open attacks. Here we analyze major blockchain-based cryptocurrencies deployed today—including Bitcoin, Ethereum, Litecoin and ZCash, determine risk exposure We finish with...

Blind quantum computation allows a client with limited capabilities to interact remote computer perform an arbitrary computation, while keeping the description of that hidden from computer. While number protocols have been proposed in recent years, little is currently understood about resources necessary accomplish task. Here, we present general techniques for upper and lower bounding communication blind use these establish concrete bounds common choices client's capabilities. Our results...

Homomorphic encryption is a form of which allows computation to be carried out on the encrypted data without need for decryption. The success quantum approaches related tasks in delegated setting has raised question whether mechanics may used achieve information-theoretically-secure fully homomorphic encryption. Here we show, via an information localization argument, that deterministic necessarily incurs exponential overhead if perfect security required.

For the last 20 years, question of what are fundamental capabilities quantum precision measurements has sparked a lively debate throughout scientific community. Typically, ultimate limits in metrology associated with notion Heisenberg limit expressed terms physical resources used measurement procedure. Over variety different were introduced, leading to confusion about meaning limit. Here, we review mainstream definitions relevant and introduce universal resource count, that is, expectation...

We set down the principles behind a modeling language for quantum software. present minimal of extensions to well-known Unified Modeling Language (UML) that allows it effectively model These are separate and independent UML as whole. As such they can be used extend any other software language, or basis completely new language. argue these both necessary sufficient model, abstractly, piece Finally, we provide small examples showcase effectiveness extension set.

Blind quantum computation allows a user to delegate an untrusted server while keeping the hidden. A number of recent works have sought establish bounds on communication requirements necessary implement blind computation, and bound based no-programming theorem Nielsen Chuang has emerged as natural limiting factor. Here we show that this constraint only holds in limited scenarios, how overcome it using novel method iterated gate teleportations. This technique enables drastic reductions...

In this paper we present a quantization of cellular automata. Our formalism is based on lattice qudits and an update rule consisting local unitary operators that commute with their own translations. One purpose model to act as theoretical quantum computation, similar the circuit model. It also shown be appropriate abstraction for space-homogeneous phenomena, such gases, spin chains, others. Some results show benefits basing are shown: universality, strong connections model, simple...

Quantum imaging promises increased performance over classical protocols. However, there are a number of aspects quantum that not well understood. In particular, it has been unknown so far how to compare and procedures. Here, we consider in single theoretical framework present general fundamental limits on the resolution deposition rate for imaging. The can be estimated from image itself. We utility function allows us protocols wide range applications.

Proof-of-Work (PoW) is a fundamental underlying technology behind most major blockchain cryptocurrencies. It has been previously pointed out that quantum devices provide computational advantage in performing PoW the context of Bitcoin. Here we make case this extends not only to all existing mechanisms, but any possible as well. This strong consequences regarding both quantum-based attacks on integrity entirety blockchain, well more legitimate uses computation for purpose mining Bitcoin and...

As progress on experimental quantum processors continues to advance, the problem of verifying correct operation such devices is becoming a pressing concern. The recent discovery protocols for computation performed by entangled but non-communicating holds promise certifying correctness arbitrary computations in fully device-independent manner. Unfortunately, all known schemes have prohibitive overhead, with resources scaling as extremely high degree polynomials number gates constituting...

We analyze a conceptual approach to single-spin measurement. The method uses techniques from the theory of quantum cellular automata correlate large number ancillary spins one be measured. It has distinct advantage being efficient: under ideal conditions, it requires application only O((3)square root N)) steps (each requiring constant rf pulses) create system N correlated spins. Numerical simulations suggest that is also, certain extent, robust against pulse errors, and imperfect initial...

The DiVincenzo criteria for implementing a quantum computer have been seminal in focussing both experimental and theoretical research information processing. These were formulated specifically the circuit model of computing. However, several new models computing (paradigms) proposed that do not seem to fit well. question is therefore what are general computers. To this end, formal operational definition introduced. It then shown according device if it obeys following four criteria: Any must...

Graphs, mathematical objects used as a ubiquitous representation of data structures, are commonly applied to better understand certain entangled states called graph states. In this insightful investigation, the authors take inverse route, and show that quantum provide an efficient way representing manipulating graphs than any possible classical structure.

Quantum engineering seeks to exploit quantum information build, among others, computing, cybersecurity, and metrology technologies. Software Engineering (QSE) focuses on the processing side of these Historically, (software) has focused development in controlled research environments 'in small'. As field progresses, we should expect see more large-scale systems be deployed as 'real-world' products services. An essential tool (classical) software been size metrics. Calculating/estimating a...

We reveal a close relationship between quantum metrology and the Deutsch-Jozsa algorithm on continuous variable systems. develop general procedure, characterized by two parameters, that unifies parameter estimation algorithm. Depending which we keep constant, procedure implements either protocol or The part of attains Heisenberg limit is therefore optimal. Due to use approximate normalizable eigenstates probabilistic. estimates value an unknown solves problem without any entanglement.

Received 28 January 2011DOI:https://doi.org/10.1103/PhysRevA.83.029903©2011 American Physical Society

In this paper we present a systematic view of Quantum Cellular Automata (QCA), mathematical formalism quantum computation. First give general framework with which to study QCA models. Then four different models, and compare them. One model discuss is the traditional QCA, similar those introduced by Shumacher Werner, Watrous, Van Dam. We also Margolus discussed Schumacher Werner. introduce two new Coloured Continuous-Time QCA. our models established proofs computational equivalence for...

Proof-of-Work (PoW) is a fundamental underlying technology behind most major blockchain cryptocurrencies. It has been previously pointed out that quantum devices provide computational advantage in performing PoW the context of Bitcoin. Here we make case this extends not only to all existing mechanisms, but any possible as well. This strong consequences regarding both quantum-based attacks on integrity entirety blockchain, well more legitimate uses computation for purpose mining Bitcoin and...

Quantum devices capable of breaking the public-key cryptosystems that Bitcoin relies on to secure its transactions are expected with reasonable probability within a decade. attacks would put at risk entire network, which has an estimated value around 500 billion USD. To prevent this threat, proactive approach is critical. The only known way any such attack upgrade currently used cryptosystems, namely ECDSA, so-called post-quantum have no vulnerabilities quantum attacks. In paper, we analyse...

Cellular Automata (CA), as they are presented in the literature, abstract mathematical models of computation. In this pa- per we present an alternate approach: using CA a model or theory physical systems and devices. While approach abstracts away all details underlying system, it remains faithful to fact that there is reality which describes. This imposes certain restrictions on types computations can physically carry out, resources needs do so. paper explore these other consequences our...