dr hab. Alexander Streltsov 

Promotor prac doktorskich
1.  20240219  Tulja Varun Kondra (Uniwersytet Warszawski)  Transformacje stanów w teorii zasobów kwantowych 
Ostatnie publikacje
1.  Chandan D.^{♦}, Tulja Varun K.^{♦}, Miller M.^{♦}, Streltsov A., Entanglement catalysis for quantum states and noisy
channels, Quantum 8, ISSN: 2521327X, DOI: 10.22331/q202403201290, Vol.8, pp.120, 2024 Streszczenie: Many applications of the emerging quantum technologies, such as quantum teleportation and quantum key distribution, require singlets, maximally entangled states of two quantum bits. It is thus of utmost importance to develop optimal procedures for establishing singlets between remote parties. As has been shown very recently, singlets can be obtained from other quantum states by using a quantum catalyst, an entangled quantum system which is not changed in the procedure. In this work we take this idea further, investigating properties of entanglement catalysis and its role for quantum communication. For transformations between bipartite pure states, we prove the existence of a universal catalyst, which can enable all possible transformations in this setup. We demonstrate the advantage of catalysis in asymptotic settings, going beyond the typical assumption of independent and identically distributed systems. We further develop methods to estimate the number of singlets which can be established via a noisy quantum channel when assisted by entangled catalysts. For various types of quantum channels our results lead to optimal protocols, allowing to establish the maximal number of singlets with a single use of the channel. Afiliacje autorów:
 140p.  
2.  Naseri M.^{♦}, Macchiavello C.^{♦}, Bruß D.^{♦}, Horodecki P.^{♦}, Streltsov A., Quantum speed limits for change of basis, NEW JOURNAL OF PHYSICS, ISSN: 13672630, DOI: 10.1088/13672630/ad25a5, Vol.26, pp.023052023052, 2024  140p.  
3.  Miller M.^{♦}, Scalici M.^{♦}, FellousAsiani M.^{♦}, Streltsov A., Power of noisy quantum states and the advantage of resource dilution, Physical Review A, ISSN: 24699926, Vol.109, pp.022404022404, 2024  100p.  
4.  Miller M.^{♦}, Scalici M.^{♦}, FellousAsiani M.^{♦}, Streltsov A., Power of noisy quantum states and the advantage of resource dilution, Physical Review A, ISSN: 24699926, DOI: 10.1103/PhysRevA.109.022404, Vol.109, pp.022404102240413, 2024 Streszczenie: Entanglement distillation allows to convert noisy quantum states into singlets, which can, in turn, be used for various quantum technological tasks, such as quantum teleportation and quantum key distribution. Entanglement dilution is the inverse process: singlets are converted into quantum states with less entanglement. While the usefulness of distillation is apparent, practical applications of entanglement dilution are less obvious. Here, we show that entanglement dilution can increase the resilience of shared quantum states to local noise. The increased resilience is observed even if diluting singlets into states with arbitrarily little entanglement. We extend our analysis to other quantum resource theories, such as quantum coherence, quantum thermodynamics, and purity. For these resource theories, we demonstrate that diluting pure quantum states into noisy ones can be advantageous for protecting the system from noise. Our results demonstrate the usefulness of quantum resource dilution, and provide a rare example for an advantage of noisy quantum states over pure states in quantum information processing. Afiliacje autorów:
 100p.  
5.  Tulja Varun K.^{♦}, Chandan D.^{♦}, Streltsov A.^{♦}, Real quantum operations and state transformations, NEW JOURNAL OF PHYSICS, ISSN: 13672630, DOI: 10.1088/13672630/acf9c4, Vol.25, pp.114, 2023 Streszczenie: Resource theory of imaginarity provides a useful framework to understand the role of complex numbers, which are essential in the formulation of quantum mechanics, in a mathematically rigorous way. In the first part of this article, we study the properties of 'real' (quantum) operations both in singleparty and bipartite settings. As a consequence, we provide necessary and sufficient conditions for state transformations under real operations and show the existence of 'real entanglement' monotones. In the second part of this article, we focus on the problem of single copy state transformation via real quantum operations. When starting from pure initial states, we completely solve this problem by finding an analytical expression for the optimal fidelity of transformation, for a given probability of transformation and vice versa. Moreover, for state transformations involving arbitrary initial states and pure final states, we provide a semidefinite program to compute the optimal achievable fidelity, for a given probability of transformation. Słowa kluczowe: resource theory of imaginarity, real quantum operations, stochastic approximate state conversion Afiliacje autorów:
 140p.  
6.  Francesco A.^{♦}, Mazelanik M.^{♦}, Lipka M.^{♦}, Streltsov A., Parniak M.^{♦}, DemkowiczDobrzański R.^{♦}, Quantum Asymmetry and Noisy Multimode Interferometry, PHYSICAL REVIEW LETTERS, ISSN: 00319007, DOI: 10.1103/PhysRevLett.128.240504, Vol.128, pp.16, 2022 Streszczenie: Quantum asymmetry is a physical resource that coincides with the amount of coherence between the eigenspaces of a generator responsible for phase encoding in interferometric experiments. We highlight an apparently counterintuitive behavior that the asymmetry may increase as a result of a decrease of coherence inside a degenerate subspace. We intuitively explain and illustrate the phenomena by performing a threemode singlephoton interferometric experiment, where one arm carries the signal and two noisy reference arms have fluctuating phases. We show that the source of the observed sensitivity improvement is the reduction of correlations between these fluctuations and comment on the impact of the effect when moving from the singlephoton quantum level to the classical regime. Finally, we also establish the analogy of the effect in the case of entanglement resource theory. Afiliacje autorów:
 200p.  
7.  Miller M.^{♦}, KangDa W.^{♦}, Scalici M.^{♦}, Kołodyński J.^{♦}, GuoYong X.^{♦}, ChuanFeng L.^{♦}, GuangCan G.^{♦}, Streltsov A., Optimally preserving quantum correlations and oherence with eternally nonMarkovian dynamics, NEW JOURNAL OF PHYSICS, ISSN: 13672630, DOI: 10.1088/13672630/ac6820, Vol.24, pp.114, 2022 Streszczenie: We demonstrate, both analytically and experimentally, the usefulness of nonMarkovianity for preserving correlations and coherence in quantum systems. For this, we consider a broad class of qubit evolutions, having a decoherence matrix separated from zero for large times. While any such Markovian evolution leads to an exponential loss of correlations, nonMarkovianity can help to preserve correlations even in the limit t → ∞. In fact, under general assumptions, eternally nonMarkovian evolution naturally emerges as the one that allows for optimal preservation of quantum correlations. For covariant qubit evolutions, we also show that nonMarkovianity can be used to preserve quantum coherence at all times, which is an important resource for quantum Słowa kluczowe: nonMarkovianity, open systems, quantum info, qubits Afiliacje autorów:
 140p.  
8.  Tanjung K.^{♦}, SuYong L.^{♦}, Changsuk N.^{♦}, Jaewan K.^{♦}, Streltsov A., Correlations and energy in mediated dynamics, NEW JOURNAL OF PHYSICS, ISSN: 13672630, DOI: 10.1088/13672630/aca9ef, Vol.24, pp.110, 2022 Streszczenie: The minimum time required for a quantum system to evolve to a distinguishable state is set by the Słowa kluczowe: quantum speed limit, quantum entanglement, mediated dynamics, correlations and energy Afiliacje autorów:
 140p.  
9.  Tulja Varun K.^{♦}, Chandan D.^{♦}, Streltsov A., Catalytic Transformations of Pure Entangled States, PHYSICAL REVIEW LETTERS, ISSN: 00319007, DOI: 10.1103/PhysRevLett.127.150503, Vol.127, pp.16, 2021 Streszczenie: Quantum entanglement of pure states is usually quantified via the entanglement entropy, the von Neumann entropy of the reduced state. Entanglement entropy is closely related to entanglement distillation, a process for converting quantum states into singlets, which can then be used for various quantum technological tasks. The relation between entanglement entropy and entanglement distillation has been known only for the asymptotic setting, and the meaning of entanglement entropy in the singlecopy regime has so far remained open. Here we close this gap by considering entanglement catalysis. We prove that entanglement entropy completely characterizes state transformations in the presence of entangled catalysts. Our results imply that entanglement entropy quantifies the amount of entanglement available in a bipartite pure state to be used for quantum information processing, giving asymptotic results an operational meaning also in the singlecopy setup. Afiliacje autorów:
 200p.  
10.  KangDa W.^{♦}, Tulja Varun K.^{♦}, Swapan R.^{♦}, Carlo Maria S.^{♦}, GuoYong X.^{♦}, ChuanFeng L.^{♦}, GuangCan G.^{♦}, Streltsov A., Operational Resource Theory of Imaginarity, PHYSICAL REVIEW LETTERS, ISSN: 00319007, DOI: 10.1103/PhysRevLett.126.090401, Vol.126, pp.09040110904017, 2021 Streszczenie: Waveparticle duality is one of the basic features of quantum mechanics, giving rise to the use of complex numbers in describing states of quantum systems and their dynamics and interaction. Since the inception of quantum theory, it has been debated whether complex numbers are essential or whether an alternative consistent formulation is possible using real numbers only. Here, we attack this longstanding problem theoretically and experimentally, using the powerful tools of quantum resource theories. We show that, under reasonable assumptions, quantum states are easier to create and manipulate if they only have real elements. This gives an operational meaning to the resource theory of imaginarity. We identify and answer several important questions, which include the stateconversion problem for all qubit states and all pure states of any dimension and the approximate imaginarity distillation for all quantum states. As an application, we show that imaginarity plays a crucial role in state discrimination, that is, there exist real quantum states that can be perfectly distinguished via local operations and classical communication but that cannot be distinguished with any nonzero probability if one of the parties has no access to imaginarity. We confirm this phenomenon experimentally with linear optics, discriminating different twophoton quantum states by local projective measurements. Our results prove that complex numbers are an indispensable part of quantum mechanics. Afiliacje autorów:
 200p.  
11.  KangDa W.^{♦}, Tulja Varun K.^{♦}, Swapan R.^{♦}, Carlo Maria S.^{♦}, GuoYong X.^{♦}, ChuanFeng L.^{♦}, GuangCan G.^{♦}, Streltsov A., Resource theory of imaginarity: Quantification and state conversion, Physical Review A, ISSN: 24699926, DOI: 10.1103/PhysRevA.103.032401, Vol.103, pp.3240113240113, 2021 Streszczenie: Complex numbers are widely used in both classical and quantum physics and are indispensable components for describing quantum systems and their dynamical behavior. Recently, the resource theory of imaginarity has been introduced, allowing for a systematic study of complex numbers in quantum mechanics and quantum information theory. In this work we develop theoretical methods for the resource theory of imaginarity, motivated by recent progress within theories of entanglement and coherence. We investigate imaginarity quantification, focusing on the geometric imaginarity and the robustness of imaginarity, and apply these tools to the state conversion problem in imaginarity theory. Moreover, we analyze the complexity of real and general operations in optical experiments, focusing on the number of unfixed wave plates for their implementation. We also discuss the role of imaginarity for local state discrimination, proving that any pair of real orthogonal pure states can be discriminated via local real operations and classical communication. Our study reveals the significance of complex numbers in quantum physics and proves that imaginarity is a resource in optical experiments. Afiliacje autorów:
 100p.  
12.  KangDa W.^{♦}, Streltsov A., Regula B.^{♦}, GuoYong X.^{♦}, ChuanFeng L.^{♦}, GuangCan G.^{♦}, Experimental Progress on Quantum Coherence: Detection,
Quantification, and Manipulation, Advanced Quantum Technologies, ISSN: 25119044, DOI: 10.1002/qute.202100040, Vol.4, pp.21000401210004016, 2021 Streszczenie: Quantum coherence is a fundamental property of quantum systems, separating quantum from classical physics. Recently, there has been significant interest in the characterization of quantum coherence as a resource, investigating how coherence can be extracted and used for quantum technological applications. In this work, the progress of this research is reviewed, focusing in particular on recent experimental efforts. After a brief review of the underlying theory, the main platforms for realizing the experiments are discussed: linear optics, nuclear magnetic resonance, and Afiliacje autorów:
 
13.  Streltsov A.^{♦}, Meignant C.^{♦}, Eisert J.^{♦}, Rates of Multipartite Entanglement Transformations, PHYSICAL REVIEW LETTERS, ISSN: 00319007, DOI: 10.1103/PhysRevLett.125.080502, Vol.125, pp.0805021 0805026, 2020 Streszczenie: The theory of the asymptotic manipulation of pure bipartite quantum systems can be considered Afiliacje autorów:
 200p.  
14.  Streltsov A., Quantum state merging with bound entanglement, NEW JOURNAL OF PHYSICS, ISSN: 13672630, DOI: 10.1088/13672630/ab70d7, Vol.22, pp.111, 2020 Streszczenie: Quantum state merging is one of the most important protocols in quantum information theory. In Słowa kluczowe: quantum entanglement, quantum communication, quantum state merging Afiliacje autorów:
 140p.  
15.  KangDa W.^{♦}, Thomas T.^{♦}, GuoYong X.^{♦}, ChuanFeng L.^{♦}, GuangCan G.^{♦}, Plenio M.^{♦}, Streltsov A., Quantum coherence and state conversion: theory and experiment, NPJ Quantum Information, ISSN: 20566387, DOI: 10.1038/s415340200250z, Vol.6, No.22, pp.19, 2020 Streszczenie: The resource theory of coherence studies the operational value of superpositions in quantum technologies. A key question in this theory concerns the efficiency of manipulation and interconversion of the resource. Here, we solve this question completely for qubit states by determining the optimal probabilities for mixedstate conversions via stochastic incoherent operations. Extending the discussion to distributed scenarios, we introduce and address the task of assisted incoherent state conversion, where the process is enhanced by making use of correlations with a second party. Building on these results, we demonstrate experimentally that the optimal stateconversion probabilities can be achieved in a linear optics setup. This paves the way towards real world applications of coherence transformations in current quantum technologies. Afiliacje autorów:
 
16.  Kołodyński J.^{♦}, Swapan R.^{♦}, Streltsov A., Entanglement negativity as a universal nonMarkovianity witness, Physical Review A, ISSN: 24699926, DOI: 10.1103/PhysRevA.101.020303, Vol.101, pp.0203031 0203035, 2020 Streszczenie: In order to engineer an open quantum system and its evolution, it is essential to identify and control the memory effects. These are formally attributed to the nonMarkovianity of dynamics that manifests itself by the evolution being indivisible in time, a property which can be witnessed by a nonmonotonic behavior of contractive functions or correlation measures. We show that by monitoring directly the entanglement behavior of a system in a tripartite setting it is possible to witness all invertible nonMarkovian dynamics, as well as all (also noninvertible) qubit evolutions. This is achieved by using negativity, a computable measure of Afiliacje autorów:
 
17.  Streltsov A., Hermann K.^{♦}, Sabine W.^{♦}, Manuel G.^{♦}, Dagmar B.^{♦}, Maximal coherence and the resource theory of purity, NEW JOURNAL OF PHYSICS, ISSN: 13672630, DOI: 10.1088/13672630/aac484, Vol.20, pp.114, 2018 Streszczenie: The resource theory of quantum coherence studies the offdiagonal elements of a density matrix in a Słowa kluczowe: quantum coherence, quantum entanglement, esource theories Afiliacje autorów:
 
18.  Regula B.^{♦}, Marco P.^{♦}, Marco C.^{♦}, Bromley T.^{♦}, Streltsov A., Gerardo A.^{♦}, Converting multilevel nonclassicality into genuine multipartite
entanglement, NEW JOURNAL OF PHYSICS, ISSN: 13672630, DOI: 10.1088/13672630/aaae9d, Vol.20, pp.033012103301213, 2018 Streszczenie: Characterizing genuine quantum resources and determining operational rules for their manipulation are crucial steps to appraise possibilities and limitations of quantum technologies. Two such key resources are nonclassicality, manifested as quantum superposition between reference states of a single system, and entanglement, capturing quantum correlations among two or more subsystems. Here we present a general formalism for the conversion of nonclassicality into multipartite entanglement, showing that a faithful reversible transformation between the two resources is always possible within a precise resourcetheoretic framework. Specializing to quantum coherence between the levels of a quantum system as an instance of nonclassicality, we introduce explicit protocols for such a mapping. We further show that the conversion relates multilevel coherence and multipartite entanglement not only qualitatively, but also quantitatively, restricting the amount of entanglement Słowa kluczowe: resource theories, quantum entanglement, nonclassicality, quantum coherence Afiliacje autorów:
 
19.  Regula B.^{♦}, Ludovico L.^{♦}, Streltsov A., Nonasymptotic assisted distillation of quantum coherence, Physical Review A, ISSN: 24699926, DOI: 10.1103/PhysRevA.98.052329, Vol.98, pp.05232910523298, 2018 Streszczenie: We characterize the operational task of environmentassisted distillation of quantum coherence under different sets of free operations when only a finite supply of copies of a given state is available. We first evaluate the oneshot assisted distillable coherence exactly, and introduce a semidefinite programming bound on it in terms of a smooth entropic quantity. We prove the bound to be tight for all systems in dimensions 2 and 3, which allows us to obtain computable expressions for the oneshot rate of distillation, establish an analytical expression for the best achievable fidelity of assisted distillation for any finite number of copies, and fully solve the problem of asymptotic zeroerror assisted distillation for qubit and qutrit systems. Our characterization shows that all Afiliacje autorów:
 
20.  Streltsov A., Swapan R.^{♦}, Boes P.^{♦}, Jens E.^{♦}, Structure of the Resource Theory of Quantum Coherence, PHYSICAL REVIEW LETTERS, ISSN: 00319007, DOI: 10.1103/PhysRevLett.119.140402, Vol.119, pp.16, 2017 Streszczenie: Quantum coherence is an essential feature of quantum mechanics which is responsible for the departure Afiliacje autorów:
 45p.  
21.  Streltsov A., Gerardo A.^{♦}, Plenio M.^{♦}, Colloquium: Quantum coherence as a resource, Reviews of Modern Physics, ISSN: 00346861, DOI: 10.1103/RevModPhys.89.041003, Vol.89, pp.0410031 04100334, 2017 Streszczenie: The coherent superposition of states, in combination with the quantization of observables, represents one of the most fundamental features that mark the departure of quantum mechanics from the classical realm. Quantum coherence in manybody systems embodies the essence of entanglement and is an essential ingredient for a plethora of physical phenomena in quantum optics, quantum information, solid state physics, and nanoscale thermodynamics. In recent years, research on the presence and functional role of quantum coherence in biological systems has also attracted considerable interest. Despite the fundamental importance of quantum coherence, the development of a rigorous theory of quantum coherence as a physical resource has been initiated only recently. This Colloquium discusses and reviews the development of this rapidly growing research field that encompasses the characterization, quantification, manipulation, dynamical evolution, and operational application of quantum coherence. Afiliacje autorów:
 
22.  Streltsov A., Swapan R.^{♦}, Manabendra Nath B.^{♦}, Lewenstein M.^{♦}, Towards Resource Theory of Coherence in Distributed Scenarios, PHYSICAL REVIEW X, ISSN: 21603308, DOI: 10.1103/PhysRevX.7.011024, Vol.7, pp.011024101102413, 2017 Streszczenie: The search for a simple description of fundamental physical processes is an important part of quantum Afiliacje autorów:
 
23.  de Vicente Julio I.^{♦}, Streltsov A., Genuine quantum coherence, JOURNAL OF PHYSICS AMATHEMATICAL AND THEORETICAL, ISSN: 17518113, DOI: 10.1088/17518121/50/4/045301, Vol.50, pp.134, 2017 Streszczenie: Any quantum resource theory is based on free states and free operations, i.e. states and operations which can be created and performed at no cost. In the resource theory of coherence free states are diagonal in some fixed basis, and free operations are those which cannot create coherence for some particular experimental realization. Recently, some problems of this approach have been discussed, and new sets of operations have been proposed to resolve these problems. We propose here the framework of genuine quantum coherence. This approach is based on a simple principle: we demand that a genuinely incoherent operation preserves all incoherent states. This framework captures coherence under additional constrains such as energy preservation and all genuinely incoherent operations are incoherent regardless of their particular experimental realization. We also introduce the full class of operations with this property, which we call fully incoherent. We analyze in detail the mathematical structure of these classes and also study possible state transformations. We show that deterministic manipulation is severely limited, even in the asymptotic settings. In particular, this framework does not have a unique golden unit, i.e. there is no single state from which all other states can be created deterministically with the free operations. This suggests that any reasonably powerful resource theory of coherence must contain free operations which can potentially create coherence in some experimental Afiliacje autorów:
 
24.  Streltsov A., Chitambar E.^{♦}, Swapan R.^{♦}, Bera M.^{♦}, Winter A.^{♦}, Lewenstein M.^{♦}, Entanglement and coherence in quantum state merging, PHYSICAL REVIEW LETTERS, ISSN: 00319007, DOI: 10.1103/PhysRevLett.116.240405, Vol.116, pp.16, 2016 Streszczenie: Understanding the resource consumption in distributed scenarios is one of the main goals of quantum information theory. A prominent example for such a scenario is the task of quantum state merging, where two parties aim to merge their tripartite quantum state parts. In standard quantum state merging, entanglement is considered to be an expensive resource, while local quantum operations can be performed at no additional cost. However, recent developments show that some local operations could be more expensive than others: it is reasonable to distinguish between local incoherent operations and local operations which can create coherence. This idea leads us to the task of incoherent quantum state merging, where one of the parties has free access to local incoherent operations only. In this case the resources of the process are quantified by pairs of entanglement and coherence. Here, we develop tools for studying this process and apply them to several relevant scenarios. While quantum state merging can lead to a gain of entanglement, our results imply that no merging procedure can gain entanglement and coherence at the same time. We also provide a general lower bound on the entanglementcoherence sum and show that the bound is tight for all pure states. Our results also lead to an incoherent version of Schumacher compression: in this case the compression rate is equal to the von Neumann entropy of the diagonal elements of the corresponding quantum state. Afiliacje autorów:
 
25.  Chitambar E.^{♦}, Streltsov A., Swapan R.^{♦}, Bera M.^{♦}, Gerardo A.^{♦}, Lewenstein M.^{♦}, Assisted Distillation of Quantum Coherence, PHYSICAL REVIEW LETTERS, ISSN: 00319007, DOI: 10.1103/PhysRevLett.116.070402, Vol.116, pp.07040210704025, 2016 Streszczenie: We introduce and study the task of assisted coherence distillation. This task arises naturally in bipartite systems where both parties work together to generate the maximal possible coherence on one of the subsystems. Only incoherent operations are allowed on the target system, while general local quantum operations are permitted on the other; this is an operational paradigm that we call local quantumincoherent operations and classical communication. We show that the asymptotic rate of assisted coherence distillation for pure states is equal to the coherence of assistance, an analog of the entanglement of assistance, whose properties we characterize. Our findings imply a novel interpretation of the von Neumann entropy: it quantifies the maximum amount of extra quantum coherence a system can gain when receiving assistance from a collaborative party. Our results are generalized to coherence localization in a multipartite setting and possible applications are discussed Afiliacje autorów:
 
26.  Streltsov A., Soojoon L.^{♦}, Gerardo A.^{♦}, Concentrating Tripartite Quantum Information, PHYSICAL REVIEW LETTERS, ISSN: 00319007, DOI: 10.1103/PhysRevLett.115.030505, Vol.115, pp.03050510305055, 2015 Streszczenie: We introduce the concentrated information of tripartite quantum states. For three parties Alice, Bob, and Afiliacje autorów:
