Shared Reference Frame Research Articles

Phase-encoded measurement device independent quantum key distribution without a shared reference frame

In this paper, a phase-encoded measurement device independent quantum key distribution (MDI-QKD) protocol without a shared reference frame is presented, which can generate secure keys between two parties while the quantum channel or interferometer introduces an unknown and slowly time-varying phase. The corresponding secret key rate and single photons bit error rate is analysed, respectively, with single photons source (SPS) and weak coherent source (WCS), taking finite-key analysis into account. The numerical simulations show that the modified phase-encoded MDI-QKD protocol has apparent superiority both in maximal secure transmission distance and key generation rate while possessing the improved robustness and practical security in the high-speed case. Moreover, the rejection of the frame-calibrating part will intrinsically reduce the consumption of resources as well as the potential security flaws of practical MDI-QKD systems.

Measurement-device-independent quantum private queries by rotation-invariant twisted photons

Quantum private query is an important cryptography protocol aiming to protect both user’s and database’s privacy. However, to execute even the simplest quantum private queries, one must establish and maintain a shared reference frame. Here we propose a rotation-invariant Measurement-device-independent quantum private queries with hybrid encoding approach, combined polarization and transverse spatial modes to overcome the polarization misalignment associated with random rotations in long-distance transmission. The initial encoding and final decoding of information in our protocol can be conveniently performed in the polarization space. Furthermore, our hybrid encoding approach only needs to insert four q-plates in practical experiment and to overcome the polarization misalignment problem.

Experimental bilocality violation without shared reference frames

Non-classical correlations arising in complex quantum networks are attracting growing interest, both from a fundamental perspective and for potential applications in information processing. In particular, in an entanglement swapping scenario a new kind of correlations arise, the so-called nonbilocal correlations that are incompatible with local realism augmented with the assumption that the sources of states used in the experiment are independent. In practice, however, bilocality tests impose strict constraints on the experimental setup and in particular to presence of shared reference frames between the parties. Here, we experimentally address this point showing that false positive nonbilocal quantum correlations can be observed even though the sources of states are independent. To overcome this problem, we propose and demonstrate a new scheme for the violation of bilocality that does not require shared reference frames and thus constitute an important building block for future investigations of quantum correlations in complex networks.

A Crossmodal Roelofs Effect Reveals a Shared Frame of Reference for Visual and Auditory Localization

A Crossmodal Roelofs Effect Reveals a Shared Frame of Reference for Visual and Auditory Localization

Quantum reference frames associated with noncompact groups: The case of translations and boosts and the role of mass

Quantum communication without a shared reference frame or the construction of a relational quantum theory requires the notion of a quantum reference frame. We analyze aspects of quantum reference frames associated with non-compact groups, specifically the group of spatial translations and Galilean boosts. We begin by demonstrating how the usually employed group average, used to dispense of the notion of an external reference frame, leads to unphysical states when applied to reference frames associated with non-compact groups. However, we show that this average does lead naturally to a reduced state on the relative degrees of freedom of a system, which was previously considered by Angelo et al. [1]. We then study in detail the informational properties of this reduced state for systems of two and three particles in Gaussian states.

Experimental verification of genuine multipartite entanglement without shared reference frames

Quantum entanglement is an essential resource for quantum information processing, either for quantum communication or for quantum computation. The multipartite case of entanglement, especially the so called genuine multipartite entanglement, has significant importance for multipartite quantum information protocols. Thus, it is a natural requirement to experimentally verify multipartite quantum entanglement when performing many quantum information tasks. However, this is often technically challenging due to the difficulty of building a shared reference frame among all involved parties, especially when these parties are distant from each other. In this paper, we experimentally verify the genuine tripartite entanglement of a three-photon Greenberger-Horne-Zeilinger state without shared reference frames. A high probability 0.79 of successfully verifying the genuine tripartite entanglement is achieved when no reference frame is shared. In the case of sharing only one common axis, an even higher success probability of 0.91 is achieved.

Experimental demonstration of genuine multipartite quantum nonlocality without shared reference frames

Multipartite quantum nonlocality is an important diagnostic tool and resource for both researches in fundamental quantum mechanics and applications in quantum information protocols. Shared reference frames among all parties are usually required for experimentally observing quantum nonlocality, which is not possible in many circumstances. Previous results have shown violations of bipartite Bell inequalities with approaching unit probability, without shared reference frames. Here we experimentally demonstrate genuine multipartite quantum nonlocality without shared reference frames, using the Svetlichny inequality. A significant violation probability of 0.58 is observed with a high-fidelity three-photon Greenberger-Horne-Zeilinger state. Furthermore, when there is one shared axis among all the parties, which is the usual case in fiber-optic or earth-satellite links, the experimental results demonstrate the genuine three-partite nonlocality with certainty. Our experiment will be helpful for applications in multipartite quantum communication protocols.

A Postscript to Panel Discussion of Gianni Nebbiosi’s “The Smell of Paper: On the Usefulness of Musical Thought in Psychoanalytic Practice”

Gianni Nebbiosi’s paper, “The Smell of Paper: On the Usefulness of Musical Thought in Psychoanalytic Practice,” explores many levels of the analyst’s clinical sensibility. These include the finding of a patient in the mind of the psychoanalyst, the discovery of new points of creative inflexion in developing metaphors with a patient who is frightened of symbolic meaning, the use of countertransference analysis to explore the analyst’s points of resistance to helping his or her patient, and the development of a creative shared frame of reference between patient and analyst that emerges from the patient’s unconscious life.

Communication between inertial observers with partially correlated reference frames

In quantum communication protocols the existence of a shared reference frame between two spatially separated parties is normally presumed. However, in many practical situations we are faced with the problem of misaligned reference frames. In this paper, we study communication between two inertial observers who have partial knowledge about the Lorentz transformation that relates their frames of reference. Since every Lorentz transformation can be decomposed into a pure boost followed by a rotation, we begin by analysing the effects on communication when the parties have partial knowledge about the transformation relating their frames, when the transformation is either a rotation or pure boost. This then enables us to investigate how the efficiency of communication is affected due to partially correlated inertial reference frames related by an arbitrary Lorentz transformation. Furthermore, we show how the results of previous studies where reference frames are completely uncorrelated are recovered from our results in appropriate limits.

Social structure, space and possession in Tongan culture and language: An ethnolinguistic study by Svenja Völkel (review)

Reviewed by: Social structure, space and possession in Tongan culture and language: An ethnolinguistic study by Svenja Völkel Alexander Mawyer Svenja Völkel. 2010. Social structure, space and possession in Tongan culture and language: An ethnolinguistic study. Culture and Language Use: Studies in Anthropological Linguistics 2. Amsterdam: John Benjamins Publishing Company. xv + 272 pp., maps, figures, tables, appendices, references, glossary, index. ISBN: cloth 978-902-72-0283-3; e-Book 978-902-72-8772-4. €95.00, $143.00. Despite common genealogy and contemporary kinship, cultural anthropologists of Oceania and Oceanic linguists do not always find opportunities for practical engagement or scholarly cross-pollination. Strikingly, this is true for empirical as well as theoretical works. Völkel’s Social structure, space and possession in Tongan culture and language: An ethnolinguistic study is a memorable recent example of a volume that establishes a shared frame of reference in its scrutiny of kinship, social order and status, spatial analysis, and possession. Moreover, the author largely succeeds in her synthetic ambition. Only the most fastidious maintainer of disciplinary boundaries could fail to be stimulated by this inquiry into the connections between culture, language, cognition, social structure, space, and possession in Tonga. Hearkening to Alessandro Duranti’s (1997) leading voice for the value and necessity of examining “language through the lenses of anthropological concern” (3), Völkel’s volume is the result of extensive work with both everyday and unusually expert Tongan speakers. It is also informed by an ethnographic sensibility to the ebb and flow of talk in the crispness of the here-and-now in a Tongan village. Moreover, the methodological stance benefits from a close and robust conversation with the long-running work at the intersection of linguistics, culture, and spatial cognition. Nine chapters explore cross-cutting dimensions of culture and language in Völkel’s attempt to “reveal and analyse a connection between Tongan language and culture for the aspects of social structure, space, and possession” (2). Nonlinguistic manifestations of cultural practice and social structure are proposed to be encoded in, expressed by, and made salient-to-context through linguistic means. Her interpretive analysis of the elaborate hierarchical character of Tongan society, for instance in kinship as cultural system and practice, exemplifies the general approach. As patterns in the lexical categorization of kin relations are brought into nuanced visibility when used to express qualities of social relationships by kin in everyday talk, Völkel is positioned to offer strong evidence for the interdependent quality of language and culture and of otherwise seemingly discrete domains therein. Moreover, Tongan language of respect—an honorific system deeply anchored in social hierarchy that encodes the system of status inequalities among relatives—beautifully supports Völkel’s sense of possibility in the scrutiny of language in use through the lens of broader anthropological concern. The volume is divided into two parts, each of three substantial chapters. Each part is bracketed by a short concluding chapter. The first chapter covers four domains of anthropological concern particularly suited to structural analysis and, as such, perhaps well selected foci for inquiry at the language-culture nexus. Ch. 2 examines Tongan social structure [End Page 614] in both micro and macro social contexts. Ch. 3 opens up a wonderful and sometimes unexpectedly intimate and occasionally visceral sense of the historical and contemporary dynamics of Tongan land tenure. Ch. 4 takes the reader into a familiar discussion of nonlinguistic possession and gift exchange in a Polynesian context in which the rights and obligations of kith and kin, of individuals and families within the cusp of society, are entangled, or to hazard a more culturally appropriate set of metaphors, into which they are woven and bound. The title of ch. 5, “Connecting remarks on social structure,” appears as something of a double entendre in as much as Völkel’s foundational observation here is of the number and variety of “linkages” or, though it is a term she does not use, the palimpsest-like quality of cultural domains of social structure, spatial organization and practice, and material possession and gift exchange. Across all of these chapters, Völkel’s suggestion of a co-determination of language in use and cultural...

Communication between general-relativistic observers without a shared reference frame

We show how to reliably encode quantum information and send it between two arbitrary general-relativistic observers without a shared reference frame. Any information stored in a quantum field will inevitably be destroyed by an unknown Bogolyubov transformation relating the observers. However certain quantum correlations between different, independent fields will be preserved, no matter what transformation is applied. We show how to efficiently use these correlations in communication between arbitrary observers.

Demonstrating genuine multipartite entanglement and nonseparability without shared reference frames

Multipartite nonlocality is of great fundamental interest and constitutes a useful resource for many quantum information protocols. However, demonstrating it in practice, by violating a Bell inequality, can be difficult. In particular, standard experimental setups require the alignment of distant parties' reference frames, which can be challenging or impossible in practice. In this work we study the violation of certain Bell inequalities, namely the Mermin, Mermin-Klyshko and Svetlichny inequalities, without shared reference frames, when parties share a Greenberger-Horne-Zeilinger (GHZ) state. Furthermore, we analyse how these violations demonstrate genuine multipartite features of entanglement and nonlocality. For 3, 4 and 5 parties, we show that it is possible to violate these inequalities with high probability, when the parties choose their measurements from the three Pauli operators, defined only with respect to their local frames. Moreover, the probability of violation, and the amount of violation, are increased when each party chooses their measurements from the four operators describing the vertices of a tetrahedron. We also consider how many randomly chosen measurement directions are needed to violate the Bell inequalities with high probability. We see that the obtained levels of violation are sufficient to also demonstrate genuine multipartite entanglement and nonseparability. Finally, we show analytically that choosing from two measurement settings per party is sufficient to demonstrate the maximum degree of genuine multipartite entanglement and nonseparability with certainty when the parties' reference frames are aligned in one direction so that they differ only in rotations around one axis.

Characterizing multipartite entanglement without shared reference frames

Multipartite entanglement constitutes one of the key resources in quantum information processing. We exploit correlation tensor norms to develop a framework for its experimental detection without the need for shared frames of reference. By bounding these norms for partially separable states and states of limited dimension we achieve an extensive characterization of entanglement in multipartite systems in an experimentally feasible way. Furthermore we show that both bi- and multipartite dimensionality of entanglement can be revealed by our methods.

Public-key cryptography based on bounded quantum reference frames

We demonstrate that the framework of bounded quantum reference frames has application to building quantum-public-key cryptographic protocols and proving their security. Thus, the framework we introduce can be seen as a public-key analogue of the framework of Bartlett et al. [1], where a private shared reference frame is shown to have cryptographic application. The protocol we present in this paper is an identification scheme, which, like a digital signature scheme, is a type of authentication scheme. We prove that our protocol is both reusable and secure under the honest-verifier assumption. Thus, we also demonstrate that secure reusable quantum-public-key authentication is possible to some extent.

Comparing Communities—The Limits of Typology

Across the disciplines, communities and identities are usually classified into general categories, such as ethnic, tribal, territorial, civic, religious or political communities/identities. This may be useful in many instances to structure the field and highlight certain distinctive features. But, as this contribution will argue, such typologies do not provide a sound basis for comparison. This holds true both for intercultural and for interdisciplinary comparison. For instance, religion was configured rather differently in ancient Rome, late Antique Christianity and early Islam, and each of them differed fundamentally from our modern concept of religion (as opposed to a secular sphere). The same applies to ethnicity. Likewise, historians and social anthropologists (and even specific schools within the disciplines) operate with often rather differently configured concepts in this area. In fact, most actual communities are framed by more than one “vision of community”; they are rarely only ethnic, religious or political. Their shared frames of reference can be compared: for instance, ancestral lineages, supernatural origins, sacred places, shared history, tribal solidarities, legal practices, exchange networks or outside perceptions. Such frames of references of course overlap and typically create more than one level of identification. This contribution will take the example of the new peoples and powers that emerged after the end of the Roman Empire in the West (such as Goths, Franks and Anglo-Saxons). What shaped these communities, and how did ethnic, territorial, religious and political identifiers interact in the process?

Implementation of High Capacity Quantum Secret Sharing Using Orbital Angular Momentum of Photons

Employing orbital angular momentum (OAM) of single photon, we demonstrate a high dimensional quantum secret sharing protocol. The protocol shows a high capacity of communication as the keys are encoded on the OAM of photons in d-level Hilbert space. In the proposed protocol, the remote users could share secret keys securely. The implementation for the OAM state preparation and measurement is also discussed. We show that the protocol exhibits a high security and the alignment of shared reference frames is not required.

Device-dependent and device-independent quantum key distribution without a shared reference frame

Standard quantum key distribution (QKD) protocols typically assume that the distant parties share a common reference frame. In practice, however, establishing and maintaining a good alignment between distant observers is rarely a trivial issue, which may significantly restrain the implementation of long-distance quantum communication protocols. Here we propose simple QKD protocols that do not require the parties to share any reference frame, and study their security and feasibility in both the usual device-dependent (DD) case—in which the two parties use well characterized measurement devices—as well as in the device-independent (DI) case—in which the measurement devices can be untrusted, and the security relies on the violation of a Bell inequality. To illustrate the practical relevance of these ideas, we present a proof-of-principle demonstration of our protocols using polarization entangled photons distributed over a coiled 10-km long optical fiber. We consider two situations, in which either the fiber spool's polarization transformation freely drifts, or randomly chosen polarization transformations are applied. The correlations obtained from measurements allow, with high probability, to generate positive asymptotic secret key rates in both the DD and DI scenarios (under the fair-sampling assumption for the latter case).

Reference-free-independent quantum key distribution immune to detector side channel attacks

Usually, a shared reference frame is indispensable for practical quantum key distribution (QKD) systems. As a result, most QKD systems need active alignment of reference frame due to the unknown and slowly variances of reference frame introduced by environment. Quite interestingly, reference-free-independent (RFI) QKD can generate secret-key bits without alignment of reference frame. However, RFI QKD may be still vulnerable to detector side channel attacks. Here, we propose a new RFI QKD protocol, in which all detector side channels are removed. Furthermore, our protocol can still tolerate unknown and slow variance of reference frame without active alignment. And a numerical simulation shows that long security distance is probable in this protocol.

Gestural Articulations of Embodied Spatiality

The work described in this paper is part of a design-based research involving the use of a game-based learning curriculum to foster students' understanding of physics concepts and principles governing the motion of charged particles in electric and magnetic fields. Students engaged in game-play and discussed the dynamics of the charged particles within the 3D game environment. The discussion sessions were video-recorded and an analysis was carried out on the gestures used by a group of students attempting to generalize their observations of the phenomena. The students’ gestures were analyzed to gain insights on their embodied sense-making of charged particle dynamics. The analysis showed that the students used gestures to (1) establish a shared frame of reference, (2) enact embodied game experience, and (3) enable the development of new understanding that surpasses their own existing vocabulary. Implications are discussed with regard to how teachers may take students’ gestures into account when facilitating the development of concepts with a strong visuo-spatial core.

Optimized state-independent entanglement detection based on a geometrical threshold criterion

Experimental procedures are presented for the rapid detection of entanglement of unknown arbitrary quantum states. The methods are based on the entanglement criterion using accessible correlations and the principle of correlation complementarity. Our first scheme essentially establishes the Schmidt decomposition for pure states, with few measurements only and without the need for shared reference frames. The second scheme employs a decision tree to speed up entanglement detection. We analyze the performance of the methods using numerical simulations and verify them experimentally for various states of two, three, and four qubits.