Universal Witness Research Articles

Scalable and effective multi-level entangled photon states: a promising tool to boost quantum technologies

Abstract Multi-level (qudit) entangled photon states are a key resource for both fundamental physics and advanced applied science, as they can significantly boost the capabilities of novel technologies such as quantum communications, cryptography, sensing, metrology, and computing. The benefits of using photons for advanced applications draw on their unique properties: photons can propagate over long distances while preserving state coherence, and they possess multiple degrees of freedom (such as time and frequency) that allow scalable access to higher dimensional state encoding, all while maintaining low platform footprint and complexity. In the context of out-of-lab use, photon generation and processing through integrated devices and off-the-shelf components are in high demand. Similarly, multi-level entanglement detection must be experimentally practical, i.e., ideally requiring feasible single-qudit projections and high noise tolerance. Here, we focus on multi-level optical Bell and cluster states as a critical resource for quantum technologies, as well as on universal witness operators for their feasible detection and entanglement characterization. Time- and frequency-entangled states are the main platform considered in this context. We review a promising approach for the scalable, cost-effective generation and processing of these states by using integrated quantum frequency combs and fiber-based devices, respectively. We finally report an experimentally practical entanglement identification and characterization technique based on witness operators that is valid for any complex photon state and provides a good compromise between experimental feasibility and noise robustness. The results reported here can pave the way toward boosting the implementation of quantum technologies in integrated and widely accessible photonic platforms.

Mission and the book of Acts in a pluralist society

A critical aspect of understanding the “missiology” of Acts is discerning the proper relationship between christology and mission practice. By analyzing the narrative construal of mission in Acts, I will show that Luke defines christology and missiology in relation to one another (Luke 24:47–49). Universal mission is not merely a secondary consequence of who Jesus is, but a basis for recognizing the full reality of Jesus’ lordship. According to Acts, the knowledge that comes with mission practice is as critical to understanding who Jesus is as understanding Jesus’ identity is a prerequisite for universal mission. This study will offer a (re)construction of mission theology for an intercultural context: first, by contesting the mission-as-mandate model that has dominated the imagination of mission practitioners; and, second, by showing how proper mission in Luke’s narrative world entails the practice of mission in which one “discovers” who Jesus is through participation in universal witness (especially to the ethnically “other”—e.g. Acts 10) rather than through imparting full knowledge to convert the other. Indeed, mission may bear an epistemological weight which, Acts suggests, radically challenges Christendom legacies of mission and offers a new foundation for mission as intercultural interdependence.

Measuring quantumness: from theory to observability in interferometric setups

We investigate the notion of quantumness based on the non-commutativity of the algebra of observables and introduce a measure of quantumness based on the mutual incompatibility of quantum states. We show that such a quantity can be experimentally measured with an interferometric setup and that, when an arbitrary bipartition of a given composite system is introduced, it detects the one-way quantum correlations restricted to one of the two subsystems. We finally show that, by combining only two projective measurements and carrying out the interference procedure, our measure becomes an efficient universal witness of quantum discord and non-classical correlations.

Witnessing arbitrary bipartite entanglement in a measurement-device-independent way

Experimental detection of entanglement of an arbitrary state of a given bipartite system is crucial for exploring many areas of quantum information processing. But such a detection should be made in a device-independent way if the preparation process of the state is considered to be faithful, in order to avoid detection of a separable state as an entangled one. The recently developed scheme of detecting bipartite entanglement in a measurement-device-independent way [Phys. Rev. Lett. 110, 060405 (2013)] does require information about the state. Here, by using Auguisiak et al.'s universal entanglement witness scheme for two-qubit states [Phys. Rev. A 77, 030301 (2008)], we provide a universal entanglement detection scheme for two-qubit states in a measurement-device-independent way. We also provide a set of universal witness operators for detecting NPT-ness (negative under partial transpose) of two-qudit states in a measurement-device-independent way. We conjecture that no such universal entanglement witness scheme exists for PPT (positive under partial transpose) entangled states. We also analyze the robustness of some of the experimental schemes---for detecting entanglement in a measurement-device-independent way---under the influence of noise in the inputs (from the referee) as well as in the measurement operator.

Eastern Orthodox Church and the Christian Mission in the Twenty-First Century

The Orthodox Church is present today all over the world, due to its mission and to the migration of the members of this church from their motherlands to the Western world. This migration took place so that its people could live in freedom, during the period of totalitarianism, or to have better conditions of life, particularly after the fall of Communism. Its mission has to be seriously taken into account in the context of Christian world mission, in order to have a relation with the living tradition of the church, on the one hand, or to know and have a vision of the doctrine of Christianity in its unity and witness in Christian history, on the other hand. By migration, the Orthodox Church became a factor in universal witness to the world as, for example, the Orthodox Romanian diaspora in the eu or usa.

Method for universal detection of two-photon polarization entanglement

Detecting and quantifying quantum entanglement of a given unknown state poses problems that are fundamentally important for quantum information processing. Surprisingly, no direct (i.e., without quantum tomography) universal experimental implementation of a necessary and sufficient test of entanglement has been designed even for a general two-qubit state. Here we propose an experimental method for detecting a collective universal witness, which is a necessary and sufficient test of two-photon polarization entanglement. It allows us to detect entanglement for any two-qubit mixed state and to establish tight upper and lower bounds on its amount. A different element of this method is the sequential character of its main components, which allows us to obtain relatively complicated information about quantum correlations with the help of simple linear-optical elements. As such, this proposal realizes a universal two-qubit entanglement test within the present state of the art of quantum optics. We show the optimality of our setup with respect to the minimal number of measured quantities.

Wheel of Life

Wheel of Life Bell Hooks (bio) 1. The wheel of life turns round and round all hope alive in still presence a steady heart of compassion sacred ritual giving peace. 2. One drop of water flowing into the ocean wet with enlightenment a taste of eternal presence of morning dew, of night fall reincarnated dream. 3. Pure aspirations dark tara jewel of the most high open the heart’s door bear universal witness. 4. True nature of self-abiding darkness and light, male and female a sacred mandala past and present a tantric path that calls and liberates all eternal Buddha. [End Page 22] 5. Thread of tantra bind mind and heart imperfect being choosing to perfect love radiance of Buddha light shining. [End Page 23] Bell Hooks bell hooks (née Gloria Jean Watkins) is among the leading public intellectuals of her generation. Her writings cover a broad range of topics including gender, race, teaching, and contemporary culture across the literary genres and include the seminal Ain’t I a Woman? Black Women and Feminism and, more recently, Appalachian Elegy: Poetry and Place. She has taught at Yale University, Oberlin College, and the City University of New York, and has served as Distinguished Professor in Residence in Appalachian Studies at Berea College since 2004. Copyright © 2015 Berea College

Conformal stealth for any standard cosmology

It is shown that any homogeneous and isotropic universe, independently of its spatial topology and matter content, allows for the presence of a conformal stealth, i.e. a nontrivial conformally invariant scalar field with vanishing energy-momentum tensor, which evolves along with the universe without causing even the smallest backreaction. Surprisingly, this gravitationally invisible universal witness is inhomogeneous with zero consequences for the underlying cosmology. Additionally, it is shown that these results are not exclusive of a four-dimensional universe by generalizing them to higher dimensions.

IN SEARCH OF MOST COMPLEX REGULAR LANGUAGES

Sequences (Ln| n ≥ k), called streams, of regular languages Lnare considered, where k is some small positive integer, n is the state complexity of Ln, and the languages in a stream differ only in the parameter n, but otherwise, have the same properties. The following measures of complexity are proposed for any stream: (1) the state complexity n of Ln, that is, the number of left quotients of Ln(used as a reference); (2) the state complexities of the left quotients of Ln; (3) the number of atoms of Ln; (4) the state complexities of the atoms of Ln; (5) the size of the syntactic semigroup of Ln; and the state complexities of the following operations: (6) the reverse of Ln; (7) the star of Ln; (8) union, intersection, difference and symmetric difference of Lmand Ln; and (9) the concatenation of Lmand Ln. A stream that has the highest possible complexity with respect to these measures is then viewed as a most complex stream. The language stream (Un(a, b, c) | n ≥ 3) is defined by the deterministic finite automaton with state set {0, 1, … , n−1}, initial state 0, set {n−1} of final states, and input alphabet {a, b, c}, where a performs a cyclic permutation of the n states, b transposes states 0 and 1, and c maps state n − 1 to state 0. This stream achieves the highest possible complexities with the exception of boolean operations where m = n. In the latter case, one can use Un(a, b, c) and Un(b, a, c), where the roles of a and b are interchanged in the second language. In this sense, Un(a, b, c) is a universal witness. This witness and its extensions also apply to a large number of combined regular operations.

Universal nonclassicality witnesses for harmonic oscillators

It is shown that a nonclassicality witness, whose expectation value can be measured for all quantum states, can be constructed from every nonclassicality filter. This finding leads to a set of universal witnesses, parameterized by only three real numbers, for the detection of nonclassicality of any quantum state of a harmonic oscillator. An explicit operator expression is given for such a universal witness. The application of the witnesses is demonstrated for a nontrivial example, and its experimental measurement is briefly considered.

A Jewish Dialogue with Howard Thurman: Mysticism, Compassion, and Community

A Jewish Dialogue with Howard Thurman: Mysticism, Compassion, and Community Edward K. Kaplan Forged in the crucible of a rural, segregated African‐American community in Florida, and nourished by closeness to the Divine Presence, the spirituality of Howard Thurman (1899‐1981) is governed by a deep, abiding inwardness, a solitary relation with God, which nourishes responsiveness to other people. He was a mystic who translated “the experience of love” into realistic, dynamic connections with fellow human beings. His ethical gift did not necessarily lead to social action, however. By temperament Thurman was not a militant. Solitude remained his distinctive mark and the slow, introverted flow of his written and spoken meditations appeals to our essential loneliness, probing our tender spots, allowing us to face pain and disenchantment with a gentle courage.1 Dialogue was Thurman’s essential mode of communication, one to one conversation, which he might then translate into prayers, sermons, meditations, or other public utterances.2 I was privileged to know Howard Thurman—and Mrs. Sue Bailey Thurman, whose vivid independence completed her husband’s optimism with a sharp critical edge. To help convey my particularly Jewish response to his thought, I share one intimate conversation with him. In 1981, I visited Dr. Thurman at his home in San Francisco. By that time he was dying from a cancer which afflicted him for several years, and I expected him to be quite weak and unable to spare much time. The opposite occurred. Thurman sat with me for over three hours and systematically asked me to review my most compelling life tasks: my divorce, my relationship with my young son, my writing, my teaching, and my mother’s recent death. At that point, I expressed my mixed feelings about her, and especially my doubt about whether she truly loved me. Thurman stared at me silently and then said, “All mothers love their children.” In anguish I asked how he could know that. “Because she gave birth to you,” he replied. I responded skeptically, “That is just a pure biological fact.” Thurman, more frail than I had ever seen him, but so much stronger than I was during those intense hours, slowly gazed at me and answered, “There is no such thing as a pure biological fact.” And still looking straight at me, he threw out his long arms and burst into exuberant laughter. I looked at this man I knew for over twenty‐five years, since my high school days, felt his deep understanding of me, and I burst into tears. Thurman’s confidence in the Divine Presence within all human beings had convinced him of my mother’s ability to love. His confidence in me challenged my ability to accept her, and to love her, as she truly was. From inwardness to compassion Beyond such individual encounters, Thurman’s skill as rhythmic, poetic writer and speaker helped form around him an interreligious, interracial and international community, from Rankin Chapel at Howard University, to the Church for the Fellowship of All Peoples in San Francisco, to Marsh Chapel at Boston University. As for my growing Jewish identity, it was Howard Thurman’s gentle, meditative style that nurtured my attraction to spirituality as such. His gentle probing put me in touch with a hunger for God. His keynote phrase, “How good it is to center down!” places us where we are, a calm amidst personal turmoil. During my high school and college years (c. 1955‐1964), conversations with Dr. and Mrs. Thurman, and steeping myself in his writings and recordings, prepared me to understand the religious thinker and social activist, Rabbi Abraham Joshua Heschel (1907–1972), Professor of Jewish Ethics and Mysticism at the Jewish Theological Seminary in New York, whom I met in 1966 while studying for a doctorate in French literature at Columbia University. Thurman’s universal witness had opened me to Heschel, who became my ancestral model. More on that later. So seductive, in fact, was Thurman’s “inward journey” (the title of his early, signature volume), that I was often tempted to remain alone, with or without God. The artist’s poetic prose and his soothing, earthy voice (available on recordings) meets us and accepts us...

Recovering the Way of Jesus in the Sermon on the Mount

In the Gospel of John, chapters 14:26 and 15:26, Jesus promises that the Father will send the Holy Spirit in Jesus? name, and the Holy Spirit ?will bring to your remembrance all that I have said to you,? and ?He will bear witness to me.? That means the Holy Spirit will surely teach us the meaning of the Sermon on the Mount--the biggest section in the New Testament of what Jesus said to us. Murray Dempster makes the point especially clearly: ?Luke made it clear in his prologue in the Acts that because of the transference of the Spirit the church continued to do and teach those things which Jesus began to do and teach (Acts 1:1). What needs to be underscored is that the message of the kingdom of God was the focal point of all those things that Jesus began to do and teach? (Dempster, Klaus, and Petersen, 23; see also Dempster, ?Pentecostal Social Concern,? 149). And Gordon Fee hammers it home with his thoroughly faithful and accurate biblical scholarship: ?The universal witness of the Synoptic tradition is that the absolutely central theme of Jesus? mission and message was ?the good news of the kingdom of God?? (in Ibid., 8). The ethics of the kingdom of God is set forth most clearly in the Sermon on the Mount. Each of the beatitudes announces a blessing of participation in the kingdom of God. The Lord?s Prayer prays for the kingdom to come. The kingdom is mentioned explicitly nine times in the Sermon. And I hope to show that each of the main teachings is a pointer to the way of deliverance that we are given when the kingdom breaks into our midst. In the Gospel of Matthew, Jesus gives us The Great Commission: ?As you go, therefore, make disciples of all peoples, baptizing them in the name of the Father, the Son, and the Holy Spirit, teaching them to practice all the commands that I have given you; and lo, I am with you always, to the close of the age.? (Matt 28:19-20). The way of discipleship and the commands of Jesus are most explicitly taught in the Sermon on the Mount. The way we are to make disciples of all peoples is to teach them the practices taught mostly in the Sermon on the Mount (Luz, Matthew 1-7, 214). The Sermon on the Mount echoes throughout the Gospel of Luke, as well as in Paul?s letters and the rest of the New Testament (Davies, Setting). In the first three centuries of the church, no other biblical passage was referred to as often as the Sermon on the Mount (Kissinger, 6). Pentecostalism is a movement of restoration of New Testament faith and practice. Therefore it is the inherent logic of Pentecostalism to pray for the help of the Holy Spirit in recovering the Sermon on the Mount for our practice. I do so pray.