Remote Parties Research Articles

Implementation of bipartite or remote unitary gates with repeater nodes

We propose some protocols to implement various classes of bipartite unitary operations on two remote parties with the help of repeater nodes in-between. We also present a protocol to implement a single-qubit unitary with parameters determined by a remote party with the help of up to three repeater nodes. It is assumed that the neighboring nodes are connected by noisy photonic channels, and the local gates can be performed quite accurately, while the decoherence of memories is significant. A unitary is often a part of a larger computation or communication task in a quantum network, and to reduce the amount of decoherence in other systems of the network, we focus on the goal of saving the total time for implementing a unitary including the time for entanglement preparation. We review some previously studied protocols that implement bipartite unitaries using local operations and classical communication and prior shared entanglement, and apply them to the situation with repeater nodes without prior entanglement. We find that the protocols using piecewise entanglement between neighboring nodes often require less total time compared to preparing entanglement between the two end nodes first and then performing the previously known protocols. For a generic bipartite unitary, as the number of repeater nodes increases, the total time could approach the time cost for direct signal transfer from one end node to the other. We also prove some lower bounds of the total time when there are a small number of repeater nodes. The application to position-based cryptography is discussed.

Rooted-tree network for optimal non-local gate implementation

A general quantum network for implementing non-local control-unitary gates, between remote parties at minimal entanglement cost, is shown to be a rooted-tree structure. Starting from a five party scenario, we demonstrate the local implementation of simultaneous control-Hermitian and multiparty control-unitary gates in an arbitrary n-party network. Previously established networks are shown to be special cases of this general construct.

Loss-tolerant state engineering for quantum-enhanced metrology via the reverse Hong-Ou-Mandel effect.

Highly entangled quantum states, shared by remote parties, are vital for quantum communications and metrology. Particularly promising are the N00N states—entangled N-photon wavepackets delocalized between two different locations—which outperform coherent states in measurement sensitivity. However, these states are notoriously vulnerable to losses, making them difficult to both share them between remote locations and recombine in order to exploit interference effects. Here we address this challenge by utilizing the reverse Hong–Ou–Mandel effect to prepare a high-fidelity two-photon N00N state shared between two parties connected by a lossy optical medium. We measure the prepared state by two-mode homodyne tomography, thereby demonstrating that the enhanced phase sensitivity can be exploited without recombining the two parts of the N00N state. Finally, we demonstrate the application of our method to remotely prepare superpositions of coherent states, known as Schrödinger's cat states.

Nonlocal hyperconcentration on entangled photons using photonic module system

Entanglement distribution will inevitably be affected by the channel and environment noise. Thus distillation of maximal entanglement nonlocally becomes a crucial goal in quantum information. Here we illustrate that maximal hyperentanglement on nonlocal photons could be distilled using the photonic module and cavity quantum electrodynamics, where the photons are simultaneously entangled in polarization and spatial-mode degrees of freedom. The construction of the photonic module in a photonic band-gap structure is presented, and the operation of the module is utilized to implement the photonic nondestructive parity checks on the two degrees of freedom. We first propose a hyperconcentration protocol using two identical partially hyperentangled initial states with unknown coefficients to distill a maximally hyperentangled state probabilistically, and further propose a protocol by the assistance of an ancillary single photon prepared according to the known coefficients of the initial state. In the two protocols, the total success probability can be improved greatly by introducing the iteration mechanism, and only one of the remote parties is required to perform the parity checks in each round of iteration. Estimates on the system requirements and recent experimental results indicate that our proposal is realizable with existing or near-further technologies.

Plug-and-play measurement-device-independent quantum key distribution

Quantum key distribution (QKD) guarantees unconditional communication security based on the laws of quantum physics. However, practical QKD suffers from a number of quantum hackings due to the device imperfections. From the security standpoint, measurement-device-independent quantum key distribution (MDI-QKD) is in the limelight since it eliminates all the possible loopholes in detection. Due to active control units for mode matching between the photons from remote parties, however, the implementation of MDI-QKD is highly impractical. In this paper, we propose a method to resolve the mode matching problem while minimizing the use of active control units. By introducing the plug-and-play (P) concept into MDI-QKD, the indistinguishability in spectral and polarization modes between photons can naturally be guaranteed. We show the feasibility of P MDI-QKD with a proof-of-principle experiment.

Measurement-Device-Independent Quantum Key Distribution over Untrustful Metropolitan Network

Unconditionally secure communication between remote parties has many applications in finance and industry. Now, a quantum key distribution network spread over a metropolitan area is shown to be secure against untrustworthy relays.

Excessive distribution of quantum entanglement

We classify protocols of entanglement distribution as excessive and non-excessive ones. In a non-excessive protocol, the gain of entanglement is bounded by the amount of entanglement being communicated between the remote parties, while excessive protocols violate such bound. We first present examples of excessive protocols that achieve a significant entanglement gain. Next we consider their use in noisy scenarios, showing that they improve entanglement achieved in other ways and for some situations excessive distribution is the only possibility of gaining entanglement.

The Role of Space in Remote Collaborations: An Exploration of Immersive Technology Attributes on Co-presence and Team Membership

GIScience 2016 Short Paper Proceedings Spatially situating remote users: An examination of immer- sive technology on presence and team participation D. Oprean 1 , M. B. Simpson 2 , A. Klippel 2 Stuckeman Center for Design Computing The Pennsylvania State University Email: dxo12@psu.edu Department of Geography The Pennsylvania State University Email: {marksimpson;klippel}@psu.edu Abstract As today’s workforce becomes more distributed, technology provides a means to communicate over long distances. This technology however offers limited forms of communication which can lead remote participants to not feel fully participant in collaborative efforts. With the re- newed interest in immersive virtual reality (iVR) technology, the promise of more affordable and better capabilities is better than ever. iVR technology can allow remote collaborators to become spatially situated in the content of a collaboration. For this work-in-progress we exam- ine levels of immersion to understand the role of co-presence for a remote participant on team membership and participation. Our experimental set up and preliminary results will be dis- cussed. Introduction In today’s workforce, technology has enabled communication and work to occur at a distance. Remote parties can easily join in meetings virtually through the use of various collaborative equipment. However, traditional audio and video technologies cannot create the full experience of being co-present in a meeting space with collaborators. With the increased capabilities, affordability, and renewed interest in immersive virtual reality (iVR) technology, the potential to spatially situate remote parties into a meeting is higher than ever. iVR technology has been a communication tool for several decades, but recent break- throughs make the hardware and software to create iVR experiences easier to use than ever before. Past research using iVR systems have examined their ability of spatially situating indi- viduals into task spaces with great success. However, these studies have examined such tech- nology through the limited scope of testing a single system. This ‘black-box’ approach to VR systems research is a limiting factor in the literature. We believe that comparing multiple iVR system aspects will allow for better connections to spatial experiences that will be generalizable to a broader scope of technology. We used our work-in-progress to address the question of how spatially present a remote collaborator feels when experiencing different levels of visual immersiveness. Specifically, this study seeks to examine the relative impact of different levels of immersive technology on spa- tial co-presence in a meeting with one remote participant. To do this, our study built on the theoretical framework and methodological approach of Balakrishnan, Oprean, Martin, and Smith (2012) to identify levels of immersiveness. Our methodological approach allowed us to address our question through examining technology affordances—the attributes of technology that allow for actions or perceptions of actions by the appropriate entity (Greeno 1994). 1.1 Presence and Immersion The nature of presence, the feeling of being ‘present’ within a given medium (Steuer 1992), in and of itself is highly subjective, making it hard to distinguish from concepts like immersion,

Testing Telepresence: Remote Reference Service via Robotics

Interacting with patrons is the heart of reference services, but it is not always possible to meet face-to-face. This paper details the results of the testing of a telepresence robot for reference services. Telepresence systems allow for two way audio and video communication between remote parties; by combining telepresence with robotics this two way communication can happen anywhere. Adding telepresence capabilities to the existing suit of reference services on offer was meant to expand the reach of librarians throughout the building. However limitations in hardware and software mean the platform is not currently sufficient for reference services.

Remotely and Conclusively Mapping One Finite Set of Qudit States onto Another Assisted by Qubit Entanglements

Alice and Bob are two remote parties. We propose a probabilistic method which allows Alice to map remotely and conclusively Bob’s set of nonorthogonal symmetric d-level quantum states onto another. The procedure we use is a remote positive operator valued measurement (POVM) in Bob’s (2d-1)-level direct sum space. We construct a quantum network for implementing this (2d-1)-level remote nonunitary POVM with (d-1) two-level remote unitary rotations. The fact that the two-level remote rotation, which is hired to rotate remotely a basis vector, can been implementing rapidly using only one ebit (a two-level Einstein-Podolsky-Rosen (EPR) pair) and one cbit (classical communication) is notable. This scheme is simpler but with less resource, which will make it more feasible and suitable for large-scale quantum network.

Conclusive qudit states transformation implemented by remote parters

Alice, Cindy, and Bob are three remote parties. We present a scheme which allows Alice and Cindy to transform probabilistically and conclusively Bobs unknown d -level quantum (qudit) state into another. In this scheme, the remote positive operator valued measurements (POVM) lies at the heart. Based on the knowledge of probability amplitudes and phase factors of Bobs original state and target state, Alice and Cindy could construct jointly the required optimal POVM, which acts remotely on Bobs (2 d -1)-dimensional direct sum space. We construct a quantum network for realizing the remote POVM with 2( d -1) remote two-level unitary rotations, and thus provide a feasible physical means to realize the remote POVM. The fact that the remote POVM could be realized using only 2( d -1) two-level Bell states (ebits) and 3( d -1) two-level classical communications (cbits) is notable. This scheme can be generalized to implement conclusively the ( N +2)-party remote qudit state transformation via ( d -1) ( N +1)-body two-level GHZ states, in which the phase factors of Bobs original state and target state are shared jointly by N agents. The success probability of implementing this remote state transformation is also investigated. This scheme is simpler but conclusive, and more efficient but with less resource, which will make it more feasible with the current experimental technology and more suitable for large-scale quantum network.

Quantum discord protection from amplitude damping decoherence.

Entanglement is known to be an essential resource for many quantum information processes. However, it is now known that some quantum features may be acheived with quantum discord, a generalized measure of quantum correlation. In this paper, we study how quantum discord, or more specifically, the measures of entropic discord and geometric discord are affected by the influence of amplitude damping decoherence. We also show that a protocol deploying weak measurement and quantum measurement reversal can effectively protect quantum discord from amplitude damping decoherence, enabling to distribute quantum correlation between two remote parties in a noisy environment.

Counterfactual quantum cryptography network with untrusted relay

Counterfactual quantum cryptography allows two remote parties to share a secret key even though a physical particle is not in fact transmitted through the quantum channel. In order to extend the scope of counterfactual quantum cryptography, we use an untrusted relay to construct a multi-user network. The implementation issues are discussed to show that the scheme can be realized with current technologies. We also prove the practical security advantages of the scheme by eliminating the probability that an eavesdropper can directly access the signal or an untrusted relay can perform false operations.

Superdense teleportation using hyperentangled photons.

Transmitting quantum information between two remote parties is a requirement for many quantum applications; however, direct transmission of states is often impossible because of noise and loss in the communication channel. Entanglement-enhanced state communication can be used to avoid this issue, but current techniques require extensive experimental resources to transmit large quantum states deterministically. To reduce these resource requirements, we use photon pairs hyperentangled in polarization and orbital angular momentum to implement superdense teleportation, which can communicate a specific class of single-photon ququarts. We achieve an average fidelity of 87.0(1)%, almost twice the classical limit of 44% with reduced experimental resources than traditional techniques. We conclude by discussing the information content of this constrained set of states and demonstrate that this set has an exponentially larger state space volume than the lower-dimensional general states with the same number of state parameters.

Deterministic Controlled Bidirectional Remote State Preparation Via a Six-qubit Maximally Entangled State

It is presented that a bidirectional remote state preparation scheme uses six-qubit maximally entangled state. In this paper we propose a new protocol which allows two distant parties to simultaneously and deterministically exchange their states under controling of a third remote party. In such a way, it cannot be successful without permission of the controller. Based on the von Neumann measurement and Bell state measurement, Alice can transmit an arbitrary single qubit state to Bob, while Bob can transmit an arbitrary single qubit state to Alice via the control of the supervisor Charlie.

Microphone cross-array beamformer processing to reduce noise and reverberation

Hands-free audio communication systems that are designed to allow audio and speech communication between remote parties are known to be sensitive to room reverberation and noise when the source is distant from the microphone. A common solution to the problem of room reverberation is to use an array of microphones to spatially filter the acoustic field. The maximum array gain is only attainable with specific microphone geometries and the gain of realizable microphone arrays is typically significantly lower than the maximum. The algorithm described in this talk attempts to address the rather slow growth in linear processing directional gain as a function of the number of microphones. One possible approach to attain higher directive gain is to use a processing scheme based on nonlinear multiplicative processing. An obvious candidate is the coherence function since it is a bounded and normalized multiplicative measure. A technique is presented for reverberation reduction processing using at least two beamforming microphones and a function of the estimated short-time coherence between the beamformer outputs. Each beamformer should have a different directional response or spatial position, or both, but with overlapping responses in the direction of the desired source.

An Architectural Assessment of Bitcoin: Using the Systems Modeling Language

Bitcoin is an emerging crypto-currency, which is wrapped in mystery and controversy. The goal is to transform how we transfer payments. The current approach for sending money from one remote party to another is via bank deposit and transfer by check or bank transfer. PayPal and other services were developed to provide faster payments to verified individuals, but each layer in the transaction adds time, cost, and/or risk to the transaction. Users of this new digital currency proclaim the benefits of security, anonymity, and efficiency for making transactions.The functionality and structure of the Bitcoin Network is complex and often attacked for not being a suitable replacement for currency. An independent understanding can be developed of the composite Bitcoin Financial Systems of Systems architecture by considering the challenges any System of System would face. A functional analysis, employing the Systems Modeling Language (SysML), is performed on the Bitcoin System of Systems architecture to help gain an understanding of the structure and functionality, and how that relates to the key actors and use cases, for determining if the users’ expectations are aligned with the architecture.

Deterministic arbitrary multi-photon entanglement sharing via noisy channels

We present an efficient strategy for sharing multipartite polarization entanglement between distant locations via the noisy channel assisted by the time-bin degree of freedom. We demonstrate an entanglement purification protocol for the three-qubit Greenberge–Horne–Zeilinger state and an entanglement distribution protocol for the three-qubit W state. We also generalize the protocol to distribute arbitrary N-photon polarization states to N distant locations. Our schemes do not consume a large number of less-entangled systems and the remote parties can share the desired state in a deterministic way with 100% fidelity in principle. These advantages make our method useful and practical in long-distance quantum communication.

Efficient single-photon-assisted entanglement concentration for an arbitrary entangled photon pair with the diamond nitrogen-vacancy center insides cavity

In this paper, a protocol for single-photon-assisted entanglement concentration is proposed. Resorting to the nonlinear optics of a nitrogen-vacancy (NV) center in a diamond embedded in a photonic crystal cavity coupled to a waveguide, remote parties can share the maximally entangled photon pair with a certain probability. Compared with other entanglement concentration protocols (ECPs), the current one does not need to know the accurate coefficients of the initial state and can be repeated to get a higher success probability. Meanwhile, this protocol is more suitable for multiphoton system concentration. All these advantages make the protocol useful in long-distance quantum communication.

Efficient nonlocal two-step entanglement concentration protocol for three-level atoms in an arbitrary less-entangledW state using cavity input-output process

We present an efficient two-step entanglement concentration protocol (ECP) for three-level atoms trapped in one-sided optical micro-cavities in an arbitrary three-particle less-entangled W state, using the coherent state input-output process in low-Q cavity quantum electrodynamics system. In each step of the new proposed protocol, one of the three remote users prepares the auxiliary coherent optical pulses to perform cavity input-output process and then utilizes the standard homodyne measurement to discriminate the final outgoing coherent states. When both of the two steps are successful, remote parties can deterministically concentrate the less-entangled W state atoms to a standard maximally entangled W state. Compared with previous ECPs for W state, this protocol has some advantages and can be widely used in current quantum repeater and some quantum information processing tasks.