In this paper, we consider hybrid quantum key distribution (QKD) networks with primarily quantum repeaters and a small number of trusted nodes. While the trusted nodes need to be trusted, the use of such nodes, together with efficient routing algorithms, can significantly improve the key generation rate. We show that when trusted nodes are placed at asymmetric locations relative to Alice and Bob, however, existing routing algorithms can lead to low key rate. To address this issue, we develop dynamic routing strategies that adjust routing decisions based on the current key pool conditions in the network. In addition, we investigate new and existing classical post-processing techniques that complement the dynamic routing strategies. Using extensive simulations, we show that our dynamic routing strategies can significantly outperform static strategies, and the post-processing techniques are beneficial in high noise scenarios. In addition, combining the dynamic routing strategies and post-processing techniques can further improve the overall key rate.

High-dimensional states (HD) are promising for quantum key distribution (QKD) due to their noise tolerance and efficiency. However, creating, and measuring, HD states is technologically challenging, thus making it important to study HD-QKD protocols where Alice and Bob are restricted in their quantum capabilities. In this paper, we revisit an HD-QKD protocol, introduced in (PRA 97 (4):042347), which does not require Alice and Bob to be capable of sending and measuring in full mutually unbiased bases. The previous proof of security for this protocol has relied on numerical methods. In this work, we provide a new proof of security, enabling the key-rate evaluation beyond previous work. Furthermore, our new proof produces better results for certain channel and dimension scenarios than prior work.

Quantum Conference Key Agreement (QCKA) protocols are designed to allow multiple parties to agree on a shared secret key, secure against computationally unbounded adversaries. In this paper, we consider a high-dimensional QCKA protocol and prove its information theoretic security against arbitrary, general, attacks in the finite-key scenario. Our proof technique may be useful for other high-dimensional multiparty quantum cryptographic protocols. Finally, we evaluate the protocol in a variety of settings, showing that high-dimensional states can greatly benefit QCKA protocols.

It has been shown recently that the framework of quantum sampling, as introduced by Bouman and Fehr, can lead to new entropic uncertainty relations highly applicable to finite-key cryptographic analyses. Here we revisit these so-called sampling-based entropic uncertainty relations, deriving newer, more powerful, relations and applying them to source-independent quantum random number generators and high-dimensional quantum key distribution protocols. Along the way, we prove several interesting results in the asymptotic case for our entropic uncertainty relations. These sampling-based approaches to entropic uncertainty, and their application to quantum cryptography, hold great potential for deriving proofs of security for quantum cryptographic systems, and the approaches we use here may be applicable to an even wider range of scenarios.

Semi-source independent quantum random number generators (SI-QRNG) are cryptographic protocols which attempt to extract random strings from quantum sources where the source is under the control of an adversary (but with known dimension) while the measurement devices are fully characterized. This represents a middle-ground between fully-trusted and full-device independence, allowing for fast bit-generation rates with current-day technology, while also providing a strong security guarantee. In this paper we analyze a SI-QRNG protocol based on quantum walks and develop a proof of security. We derive a novel entropic uncertainty relation for this application which is necessary since standard relations actually fail in this case.

In this paper we derive a key rate expression for the extended version of the B92 quantum key distribution protocol that takes into account, for the first time, the effects of operating with finite resources. With this expression, we conduct an analysis of the protocol in a variety of different noise and key- length settings, and compare to previous bounds on comparable protocols.

In this paper we derive a new quantum entropic uncertainty relation, bounding the conditional smooth quantum min entropy based on the result of a measurement using a two outcome POVM and the failure probability of a classical sampling strategy. Our relation works for systems of arbitrary dimension. We apply it to analyze a new source independent quantum random number generation protocol and show our relation provides optimistic results compared to prior work.

In this work we introduce a novel QKD protocol capable of smoothly transitioning, via a user-tuneable parameter, from classical to semi-quantum in order to help understand the effect of quantum communication resources on secure key distribution. We perform an information theoretic security analysis of this protocol to determine what level of "quantumness" is sufficient to achieve security, and we discover some rather interesting properties of this protocol along the way.

In this paper we show how genetic algorithms can be effectively applied to study the security of arbitrary quantum key distribution (QKD) protocols when faced with adversaries limited to current-day technology. We compare two approaches, both of which take into account practical limitations on the quantum power of an adversary (which can be specified by the user). Our system can be used to determine upper-bounds on noise tolerances of novel QKD protocols in this scenario, thus making it a useful tool for researchers. We compare our algorithm's results with current known numerical results, and also evaluate it on newer, more complex, protocols where no results are currently known.

In this paper we present a new proof technique for semi-quantum key distribution (SQKD) protocols which makes use of a quantum entropic uncertainty relation to bound an adversary's information. We develop several new techniques for analyzing SQKD protocols; furthermore, our new proof may hold application in the security analysis of other semi-quantum protocols or protocols relying on two-way quantum communication.

A semi-quantum key distribution (SQKD) protocol allows a quantum user and a limited "classical" user to establish a shared secret key secure against an all-powerful adversary. In this work, we present a new SQKD protocol where the quantum user is also limited in her measurement capabilities. We describe the protocol, perform an information theoretic analysis of its security, and show its noise tolerance is as high as "fully quantum" QKD protocols.

Quantum Key Distribution (QKD) allows two parties to establish a shared secret key secure against an all-powerful adversary. Typically, one designs new QKD protocols and then analyzes their maximal tolerated noise mathematically. If the noise in the quantum channel connecting the two parties is higher than this threshold value, they must abort. In this paper we design and evaluate a new real-coded Genetic Algorithm which takes as input statistics on a particular quantum channel (found using standard channel estimation procedures) and outputs a QKD protocol optimized for the specific given channel. We show how this method can be used to find QKD protocols for channels where standard protocols would fail.

In this paper we show how a genetic algorithm may be used to analyze the security of quantum key distribution (QKD) protocols. In particular, we construct an algorithm to find the maximally tolerated noise level of a QKD protocol (the threshold after which users must abort). Extending on our previous work in this area, we describe in detail the algorithm and how it is constructed. We show how preprocessing may be considered by the algorithm to improve this tolerated bound. Finally, we evaluate it on multiple QKD protocols, comparing it to known bounds and also discovering new results. We also show how it can be used to analyze the security of complicated QKD protocols requiring the adversary to interact with the users. It may also be used to detect security flaws in protocols. Our algorithm can be a useful tool in QKD research and design.

In this paper we consider a three-state variant of the BB84 quantum key distribution (QKD) protocol. We derive a new lower-bound on the key rate of this protocol in the asymptotic scenario and use mismatched measurement outcomes to improve the channel estimation. Our new key rate bound remains positive up to an error rate of 11%, exactly that achieved by the four-state BB84 protocol.

Semi-quantum key distribution protocols are designed to allow two users to establish a secure secret key when one of the two users is limited to performing certain “classical” operations. There have been several such protocols developed recently, however, due to their reliance on a two-way quantum communication channel (and thus, the attacker's opportunity to interact with the qubit twice), their security analysis is difficult and little is known concerning how secure they are compared to their fully quantum counterparts. In this paper we prove the unconditional security of a particular semi-quantum protocol and derive an expression for its key rate, in the asymptotic scenario.

In this paper we are interested in examining some of the benefits of combining artificial life with quantum decision making. After providing an introduction to quantum computing, we attempt to decompose and list those features of a quantum decision maker which we believe are important to an artificial life form, and, from this, we describe a simple abstract interface for such a decision maker. Following this, we describe how a quantum decision maker, supporting such an interface, may be used to operate artificial life forms. We conclude by describing our own experiments in this field including quantum flocking behaviors and robotics. In both cases we will observe complex and interesting behaviors arise from the quantum model despite being given very basic behavioral rules.

In this paper we apply a real-time evolving neural network which uses a hill-climbing algorithm capable of adapting not only a network’s synaptic weights but also its topology (creating a recurrent neural network). We then apply this network to a robot in a simulated environment. By equipping the robot with a minimal set of instincts and a short-term memory system (to facilitate reinforcement learning), we observe that several strategies developed which pass the emergent behavior test of (Ronald et al., 1999). In particular, we see robots learning behaviors that are not rewarded by the environment. Of course a hill-climbing algorithm is more likely than a genetic-algorithm to get stuck at a local optimum, we argue that, despite this, the method described here has several unique advantages. In particular, it allows us to create a single persistent robot that slowly learns and “grows up ” as described in (Ross et al., 2003). With our system, it is an individual that learns not a population of individuals, and our learning is continual (e.g. there is no need to reset the robot to some starting position to evaluate the fitness of a particular network). We conclude with several future problems and applications. For instance, we describe a simple mechanism allowing a network to be copied to embedded hardware whenever a network connection is available to a PC (which is responsible for the memory and time intensive task of evolving the network). This mechanism does not require a continual link to a PC. We also discuss the possibility of creating a distributed evolving neural network system.