Temporal Entanglement Research Articles

Wavepacket interference of two photons through a beam splitter: from temporal entanglement to wavepacket shaping

Quantum interferences based on beam splitting are widely used for entanglement. However, the quantitative measurement of the entanglement in terms of temporal modes and wavepacket shaping facilitated by this entanglement remain unexplored. Here we analytically study the interference of two photons with different temporal shapes through a beam splitter (BS) and then propose its application in temporal entanglement and shaping of photons. The temporal entanglement described by Von Neumann entropy is determined by the splitting ratio of BS and temporal indistinguishability of input photons. We found that maximum mode entanglement can be achieved with a 50/50 BS configuration, enabling the generation of a Bell state encoded in temporal modes, independent of the exact form of the input photons. Then, detecting one of the entangled photons at a specific time enables the probabilistic shaping of the other photon. This process can shape the exponentially decaying (ED) wavepacket into the ED sine shapes, which can be further shaped into Gaussian shapes with a fidelity exceeding 99%. The temporal entanglement and shaping of photons based on interference may solve the shape mismatch issues in large-scale optical quantum networks.

Temporal entanglement barriers in dual-unitary Clifford circuits with measurements

We study temporal entanglement in dual-unitary Clifford circuits with probabilistic measurements preserving spatial unitarity. We exactly characterize the temporal entanglement barrier in the measurement-free regime, exhibiting ballistic growth and decay and a volume-law peak. In the presence of measurements, we relate the temporal entanglement to the scrambling properties of the circuit. For “good scramblers” measurements do not qualitatively change the temporal entanglement profile but only result in a reduced entanglement velocity, whereas for “poor scramblers” the initial ballistic growth of temporal entanglement with bath size is modified to diffusive. This difference is understood through a mapping of the underlying operator dynamics to a biased and an unbiased persistent random walk, respectively. In the latter case measurements additionally modify the ballistic decay to the perfect dephaser limit, with vanishing temporal entanglement, to an exponential decay, which we describe through a spatial transfer matrix method. This spatial dynamics is shown to be described by a non-Hermitian hopping model, exhibiting a PT-breaking transition at a critical measurement rate p=1/2. In all cases the peak value of the temporal entanglement barrier exhibits volume-law scaling for all measurement rates. Published by the American Physical Society 2024

Space and Time Correlations in Quantum Histories

AbstractThe formalism of generalized quantum histories allows a symmetrical treatment of space and time correlations, by taking different traces of the same history density matrix. In this framework, the characterization of spatial and temporal entanglement is revisited. An operative protocol is presented, to map a history state into the ket of a static composite system. It is demonstrated, by examples, how the Leggett–Garg and the temporal Clauser‐Horne‐Shimony‐Holt (CHSH) inequalities can be violated in this approach.

Entanglement membrane in exactly solvable lattice models

Entanglement membrane theory is an effective coarse-grained description of entanglement dynamics and operator growth in chaotic quantum many-body systems. The fundamental quantity characterizing the membrane is the entanglement line tension. However, determining the entanglement line tension for microscopic models is in general exponentially difficult. We compute the entanglement line tension in a recently introduced class of exactly solvable yet chaotic unitary circuits, so-called generalized dual-unitary circuits, obtaining a nontrivial form that gives rise to a hierarchy of velocity scales with vE<vB. For the lowest level of the hierarchy, L¯2 circuits, the entanglement line tension can be computed entirely, while for the higher levels the solvability is reduced to certain regions in spacetime. This partial solvability enables us to place bounds on the entanglement velocity. We find that L¯2 circuits saturate certain bounds on entanglement growth that are also saturated in holographic models. Furthermore, we relate the entanglement line tension to temporal entanglement and correlation functions. We also develop methods of constructing generalized dual-unitary gates, including constructions based on complex Hadamard matrices that exhibit additional solvability properties and constructions that display behavior unique to local dimension greater than or equal to three. Our results shed light on entanglement membrane theory in microscopic Floquet lattice models and enable us to perform nontrivial checks on the validity of its predictions by comparison to exact and numerical calculations. Moreover, they demonstrate that generalized dual-unitary circuits display a more generic form of information dynamics than dual-unitary circuits. Published by the American Physical Society 2024

Migrant workers within the platform assemblage: entwined temporalities of gig work and the border regime

ABSTRACT The temporal structuring of migrant gig workers’ work and lives has been insufficiently addressed in research. Drawing on multi-sited onlineoffline methodologies, including interviews with migrants working via location-based work platforms (cleaning, food delivery) in Finland, we propose the term platform assemblage to analyse the temporal entanglements of living labour, work platforms and the border regime. We argue that migrant gig workers’ entanglement in the platform assemblage engenders experiences of constraint, not only via formally weak labour market positions but also through the specific temporalities arising in the complex entwinement of algorithms, the varying digital platforms used, ratings, urban interferences, migratory status and the personal resources required to navigate these constraints. Discerning the relationship between migrants’ encounters with the temporal border regime, the temporal organisation of platform work, and migrants’ contestations over the dynamics of work, the article contributes to the emerging literature on migrant gig workers.

Temporal entropy and the complexity of computing the expectation value of local operators after a quench

We study the computational complexity of simulating the time-dependent expectation value of a local operator in a one-dimensional quantum system by using temporal matrix product states(MPSs) and argue that it is intimately related to that of encoding temporal transition matrices and their partial traces. We show that we can upper-bound the rank of these reduced transition matrices by one of the Heisenberg evolution of local operators, thus making aconnection between two apparently different quantities, the temporal entanglement and the local operator entanglement(OE). As a result, whenever the local OE grows slower than linearly in time, we show that computing time-dependent expectation values of local operators using temporal MPSs is likely advantageous with respect to computing the same quantities using standard MPS techniques. Published by the American Physical Society 2024

Temporal entanglement entropy as a probe of renormalization group flow

The recently introduced concept of timelike entanglement entropy has sparked a lot of interest. Unlike the traditional spacelike entanglement entropy, timelike entanglement entropy involves tracing over a timelike subsystem. In this work, we propose an extension of timelike entanglement entropy to Euclidean space (“temporal entanglement entropy”), and relate it to the renormalization group (RG) flow. Specifically, we show that tracing over a period of Euclidean time corresponds to coarse-graining the system and can be connected to momentum space entanglement. We employ Holography, a framework naturally embedding RG flow, to illustrate our proposal. Within cutoff holography, we establish a direct link between the UV cutoff and the smallest resolvable time interval within the effective theory through the irrelevant \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$T\\overline{T }$$\\end{document} deformation. Increasing the UV cutoff results in an enhanced capability to resolve finer time intervals, while reducing it has the opposite effect. Moreover, we show that tracing over a larger Euclidean time interval is formally equivalent to integrating out more UV degrees of freedom (or lowering the temperature). As an application, we point out that the temporal entanglement entropy can detect the critical Lifshitz exponent z in non-relativistic theories which is not accessible from spatial entanglement at zero temperature and density.

The mobility biography of things and the climate emergency

This article examines the potential of the ‘biography of things’ to enhance mobility studies in the context of the climate emergency of the Anthropocene. It suggests that mobility research should thoroughly consider non-human entities to address this unprecedented crisis. To achieve this goal, the article draws on anthropological literature about the biography of things and new materialist discourses about non-human agency. The text begins by exploring vitalism as a philosophical foundation for investigating the agency of things and their relationship to the biography of things in mobility studies. To address this issue, the ‘mobility biography of things’ methodology is proposed as a valuable approach. This methodology acknowledges the agency and ‘personhood’ of non-human entities, revealing the temporal and spatial entanglement of things by studying their mobility throughout their lifespan. It can derive ethical and political significance without strict boundaries between the social and natural worlds.

‘Dead faces laugh’: Medievalist hungers and Irish republican time, 1917-1981

AbstractThe article analyses the temporal entanglements of personal and historical time through hunger-striking protests in Ireland and their commemoration in medieval imagery, reflecting on the role of medievalism and temporality in nation-building by insurgent agents. Between 1917 and 1981, twenty-two Irish republican paramilitary prisoners undertook hunger strikes to the death for recognition of political status and protest against their prison regimes. While some of these deaths went unremarked by the wider public because of state censorship and lack of support, others catalysed worldwide attention, and succeeded in pitching a compelling national and political narrative for their supporters. The article focuses on how the use of medievalism in examining and commemorating these deaths highlights the vivid temporal collapse between the present of the individual and the past of the nation, and the way this can appeal to the protest’s audience, while making a powerful political bid for the legitimacy of the insurgents’ national narrative. The article examines temporal entanglement both as practiced by the audience of the hunger strikes, from poets such as W.B. Yeats and Seamus Heaney to journalists and scholars, and by the republican community itself, whether by hunger strike survivors, their comrades, or their families, bringing together literary, material, and art historical evidence to show its relevance and pervasiveness. By doing so, the article achieves a study of the ways medievalist temporalities interact with political and personal history, in a bid for the ownership and definition of the nation.

Geographies of storage

AbstractResource storage has long played a key role in the production of socio‐ecological arrangements and economic relations. Even so, storage as a concept has remained somewhat marginal within geographical scholarship, often obscured by an analytical focus on the dynamics of movement. Reviewing recent works from geography, science and technology studies, and anthropology that center sites and practices of storage, this essay elaborates the diverse ways in which storage arrangements mediate resource circulation and the production of space. This literature demonstrates that thinking systematically with storage can illuminate a range of novel temporal, material, and value entanglements in‐the‐making, pointing to potentially fruitful avenues for future research.

Re-forming resource entrepôts: Urban investment, extraction, and Beira’s Grande and Golden Peacock Hotels

Recent literature on investment and African infrastructure have called for examining ‘Global China’s’ urban impacts. This article investigates these in the entrepôt city of Beira, Mozambique, offering an approach to urban investment that centers cities’ rural-urban, and historically entangled connections. Through what I term ‘vertical’ and ‘horizontal’ aspects, I introduce an analytical and conceptual approach to attend to these temporal and spatial dynamics of not only city-making, but capitalist-oriented, extractivist place-making. Analyzing a set of historical and colonial hotels and special economic zones (SEZs), I demonstrate how, rather than being a Chinese model for implementation in various locales, new Mozambican-Chinese projects in Beira articulate with and create new spatial connections that are innately interlinked with European extractive practices and designs. I also de-center the city, demonstrating how urban space is reconfigured through its relationship with its outsides, rather than the other way around. By investigating Beira as a re-forming resource entrepôt, I challenge the above scholarship to take seriously deeper histories of infrastructure investment in Africa, and attend to the inextricable nature of especially city-hinterland regional ties. Ultimately, I examine temporal and spatial entanglements of capitalist extraction, entrepôt construction, and Southern African urbanism, through a historically situated and regional view.

Survivor Testimonies and the Problem of Time

Testimonies of Holocaust survivors have had an essential influence on public engagement with the Shoah in recent decades. Given this importance, the imminent end of the “era of the witness” has sparked fears that the history of the Holocaust could soon be forgotten. The past decades have therefore seen unprecedented efforts to record the testimonies of Holocaust survivors in order to safeguard the immediacy of their accounts. In this essay, I trace how different temporal entanglements have affected the narrated memory of Holocaust survivors and thus also shaped the knowledge of those born later. Focusing on four interviews conducted with a Jewish Holocaust survivor in 1946, 1995, 1998, and 2004 respectively, I explore how biological time, historical time, recording time, and the temporality of narrative have shaped the narrated memories. As I argue, the different temporal entanglements have allowed for starkly different reconfigurations and reconstructions of the past. This renders the study of the epistemic constitutive nature of entangled temporalities important not only for Holocaust studies, but also for the history of knowledge, a field which has recently turned to processes of forgetting and ignorance.

Equilibration of multitime quantum processes in finite time intervals

A generic non-integrable (unitary) out-of-equilibrium quantum process, when interrogated across many times, is shown to yield the same statistics as an (non-unitary) equilibrated process. In particular, using the tools of quantum stochastic processes, we prove that under loose assumptions, quantum processes equilibrate within finite time intervals. Sufficient conditions for this to occur are that multitime observables are coarse grained in both space and time, and that the initial state overlaps with many different energy eigenstates. These results help bridge the gap between (unitary) quantum and (non-unitary) statistical physics, i.e., when all multitime properties and correlations are well approximated by stationary quantities, which includes non-Markovianity and temporal entanglement. We discuss implications of this result for the emergence of classical stochastic processes from multitime measurements of an underlying genuinely quantum system.

A Matter of Time: Anticipation Work and Digital Temporalities in Refugee Humanitarian Assistance in Turkey

Scholarly work interrogating time and temporality in CSCW predominantly focuses on the temporal coordination of work in high-resource settings and is usually based in Global North. This paper aims to complicate and complement this scholarship by investigating the temporal entanglements of digital humanitarian work with refugees and asylum seekers in Turkey during COVID-19. We interviewed 22 humanitarian workers to understand their experiences and concerns as well as strategies they employed to support refugees and immigrants at a distance. The data reveal the complex temporal, informational, and infrastructural dimensions of technologically-mediated refugee support work, challenging the trope of "pivot to remote work", as popular in western countries. Our findings contribute to the CSCW research on the theory of anticipation work and its relationship with the concept of collaborative rhythms to explicate the relational and situated aspects of the temporal experiences of humanitarian workers in low-resource settings.

Precarious Bodies in Precarious Times: Herstorical Transcorporeality in Emma Donoghue’s The Pull of the Stars

This article draws on the intersection of the metahistorical, corporeal and material turn in contemporary cultural theory, with a focus on Emma Donoghue’s novel The Pull of the Stars (2020), incidentally written to commemorate a centenary of the Spanish flu in Britain, and suddenly appearing prophetic of the COVID-19 situation in 2020–2021, with unintentional, but poignant parallels. The methodological framework used for the article is transmodern metahistory, as well as new materialism, with its important concepts of transcorporeality (Alaimo) and intra-action (Barad). The article examines women’s (bodily) lives in 1918 Dublin as depicted in the novel, against the tempestuous political and military historical context furnishing the background for the material, temporal and discursive entanglements and shared vulnerabilities, which are the centre of the narrative. It also touches upon topical issues and processes characterizing the present-day world, such as the global COVID-19 pandemic, #MeToo and BLM movements, social injustice and intersectional feminism, as well as silenced traumatic historical phenomena, such as the cruelty and abuse of Irish and Canadian residential institutions, and the larger issue of livable lives—a crucial topic for women writers today.

Coordination mechanisms and the role of taskscape in value co-creation: The British ‘milkman’

Service-dominant (S-D) logic holds that coordination mechanisms contribute to value cocreation. This research explores everyday social interaction processes in Britain's nocturnal, recurrent milk doorstep-delivery service. It uses ethnographic fieldwork with service providers (‘milkmen’) and semi-structured customer interviews and online feedback to enrich understandings.Space-time-culture dimensions are linked with existing S-D logic conceptions of value cocreation. Using Ingold’s (1993) perspective, the doorstep becomes a taskscape, with dwelling activities, a temporality of rhythmic interrelations, and patterns of resonance – uniting practices and institutions.(Interactive) dwelling activities, (reliable) rhythms, and (contextual) romanticization are the central coordination mechanisms in this iconic service, and shape micro-, meso- and macro-level interactions. Their effect on value cocreation is considerable as they derive from mutual projections, reflections, and individual understandings of customers’ doorsteps as shared- temporally-located interaction taskscapes. This realizes value cocreation as part of the life of the world, performed amid its material, temporal and social entanglements.

African Ecomedia: Network Forms, Planetary Politics By Cajetan Iheka

Reviewed by: African Ecomedia: Network Forms, Planetary Politics by Cajetan Iheka Christopher R. Hebert African Ecomedia: Network Forms, Planetary Politics BY CAJETAN IHEKA Duke UP, 2021. xiii + 322 pp. ISBN 9781478014744 paper. Cajetan Iheka's African Ecomedia, his first full-length work following Naturalizing Africa (2017), is a continuation of his focus on the intersection between African cultural expression and environmental issues on the continent. Unlike Naturalizing Africa, which discusses literary texts across a broad geographical range, African Ecomedia turns toward visual culture, to include films (both documentary and fictional), photographs, sculpture, and video art. Iheka broadly demarcates the "media" within this book into three different kinds: media arts (film, photography), resource media (oil, uranium), and elemental media (earth, air, water, fire) (8). Importantly, these three kinds of media are linked through transnational networks that often prioritize Western consumption over the ecological health of African environments and the well-being of African laborers who work with e-waste or dangerous resource media. By foregrounding these different kinds of media as well as their networks of production and consumption, African [End Page 190] Ecomedia broadly expands the purview of the environmental humanities and provides a framework for a nuanced discussion of media in a world that is radically interconnected. Iheka's task in this work, therefore, is not only to explicate different representations of the environment in African visual culture, but also to untangle the complicated itineraries of media in all its materiality on the African continent. Iheka's first chapter opens with a discussion of Wanuri Kahiu's film Pumzi and Fabrice Monteiro's photographic collection The Prophecy from the perspective of temporal entanglement. By calling attention to the ways in which these artists incorporate elements of the past in their new-media creations, Iheka identifies important threads of continuity between ecological attitudes of the past and those of an imagined future, most interestingly through the waste aesthetics of Monteiro's photographs. His second and third chapters approach environmental issues in various films and photography collections through the idea of spatial entanglement—for example, excessive consumption of electronic goods in Europe and North America directly contributes to rapidly growing e-waste sites in Ghana, just as a thirst for oil in the industrial centers of the Global North has traumatizing effects on resource centers in Africa, particularly the Niger Delta region. His examination of Pieter Hugo's photography collection Permanent Error in chapter two is especially salient, as he deftly analyzes the photos of burning waste in Agbogbloshie not as "poverty porn" but to explain the "logics of exploitation" that the images reveal (66). Iheka's fourth chapter focuses on the circulation of a grisly safari trophy-photo shortly after the death of Cecil the Lion and, importantly, during the Black Lives Matter protests in 2015. This photo and its viral trajectory "allows for apprehending vulnerabilities across species" (153). In this chapter, Iheka also calls for more attention toward "interspecies entanglement"—and he cites Orlando von Einsiedel's film Virunga as a positive example of media that "activates a borderland for intertwining human-nonhuman interests" (153). Finally, his fifth chapter explores African cities and their urban spaces as sites of precarity as well as sustainability. His analysis of Wu Jing's Wolf Warrior 2, a Chinese film set in an African city, is especially interesting as it underscores the struggle for influence in Africa between China and the West, as well as the racist ideologies at the heart of much media that takes Africa as its subject. As he notes, "in every battle in which elephants fight, the grass—in this case the African space and the continent's inhabitants—suffers" (207). One of the biggest strengths of Iheka's work in African Ecomedia is his commitment to a practice of what he calls insightful reading—a way of responsibly engaging with media arts that depict ecological degradation and human suffering. For example, Iheka does not turn away from the haunting photographs of young Ghanaian e-waste workers in Pieter Hugo's Permanent Error, nor does he downplay the future trauma that ordinary people will experience in the Niger Delta or in Arlit, where oil exploration and the mining of...

Overcoming the entanglement barrier in quantum many-body dynamics via space-time duality

Describing nonequilibrium properties of quantum many-body systems is challenging due to high entanglement in the wave function. We describe the evolution of local observables via the influence matrix (IM), which encodes the effects of a many-body system as an environment for local subsystems. Recent works found that in many dynamical regimes the IM of an infinite system has low temporal entanglement and can be efficiently represented as a matrix-product state (MPS). Yet, direct iterative constructions of the IM encounter highly entangled intermediate states---a temporal entanglement barrier (TEB). We argue that TEB is ubiquitous, and elucidate its physical origin via a semiclassical quasiparticle picture that exactly captures the behavior of integrable spin chains. Further, we show that a TEB also arises in chaotic spin chains, which lack well-defined quasiparticles. Based on these insights, we formulate an alternative light-cone growth algorithm, which provably avoids TEB, thus providing an efficient construction of the thermodynamic-limit IM as a MPS. This work uncovers the origin of the efficiency of the IM approach for studying thermalization and transport.

African Ecomedia: Network Forms, Planetary Politics by Cajetan Iheka

Reviewed by: African Ecomedia: Network Forms, Planetary Politics by Cajetan Iheka Sheila Petty (bio) African Ecomedia: Network Forms, Planetary Politics by Cajetan Iheka. Duke University Press. 2021. 336 pages. $104.95 hardcover; $27.95 paper; also available in e-book. Cajetan Iheka’s outstanding book on environmental issues in African visual culture and screen media paves the way for scholarship in African ecocritical studies. Organized into five chapters, an introduction, and an epilogue, African Ecomedia: Network Forms, Planetary Politics shows how, through film, video art, photography, sculpture, and other media, African artists deliver a unique perspective on the socioecological costs of media production, from mineral and oil extraction to the politics of animal conservation. What, for Africa, Iheka asks, is the price of “the ecological footprint of media”?1 He posits that Africans “are disproportionately affected by the distribution of ecological risks” and calls for “empathetic labor” that “is nonexploitative, and is calibrated around the flourishing of various life forms in Africa and beyond.”2 Iheka’s work underscores the significance of African cultural artifacts and their centrality in ecomedia studies and provides a model for twenty-first-century ecological media studies that combine media arts, resource media, and elemental media (e.g., fire, air, water, and earth). The author’s main goal is to expose a grand narrative of global entanglements and to uncover the ecological, social, and human expense to Africa of production and consumption of global media. Iheka’s project probes the implications of resource extraction on the African continent and the ethics of presenting [End Page 204] these images to the world. His methodology constitutes an approach he calls “insightful reading,” which is contextual, located in historical and environmental frames, and allows for consideration of an image’s deep structure through holistic analysis of its cinematic properties.3 In chapter 1, Iheka is concerned with temporal entanglements, which he explores through Wanuri Kahiu’s short science fiction film Pumzi (2009) and Fabrice Monteiro’s series of photographs titled The Prophecy (2015). He argues that both media examples draw on previous African traditions and myths specific to their cultures and blend conventions of artistic genres, African philosophy, and supernatural beliefs. Although Iheka relies somewhat on the Afrofuturism discourse of Mark Dery and Alondra Nelson in this chapter, he is careful to not allow African Indigenous concerns to be overshadowed by the African American frame of Afrofuturism.4 He further asserts that both artists foreground the aesthetics of waste recycling and recuperation. Iheka regrets that Pumzi’s emancipatory thrust is overshadowed by the sacrifice the main character Asha (Kudzani Moswela) must make of her life in order to counter the death of a tree. Monteiro’s photographs foreground their constructed nature by showing extra-human African figures maneuvering through post-apocalyptic backgrounds that include oceans, junkyards, and masses of trash. The figures are clothed in nets, cables, and other objects salvaged from oceans and landfills. Iheka maintains that these artists’ works proffer a culture of hope through recycling and reuse. He further proffers that these works constitute the fruits of a shriving process on the part of the artists as they work through and past complicated traumas of racial, cultural, and global magnitude. Chapter 2 extends Iheka’s discussion of temporal networks by reading spatial interconnections in Pieter Hugo’s series of photographs titled Permanent Error (2011), which depicts recycling of electronic waste in Agbogbloshie, Ghana, and Franck Bieleu’s documentary film The Big Banana (2011), which documents the workings of a transnational banana plantation in Cameroon. The author takes up the issue of labor and its various entangled forms of exploited African unwaged and digital labor that enable planetary communications technology. Chapter 3 extends this theme by probing the ecological and human trauma produced by resource extraction in Nigeria (oil) and Niger (uranium). Michael Watt and Ed Kashi’s Curse of the Black Gold (2008), a collaborative work of fiction, poetry, essays, photographs, interviews, and a letter, “paints the image of a future tainted by oil toxicity” in the Niger Delta, while Idrissou Mora-Kpai’s film Arlit, deuxième Paris (Arlit: The Second Paris, 2005) depicts how extractive uranium strip mining in the town of Arlit...

Temporal entanglements in art and exhibition histories

Temporal entanglements in art and exhibition histories