We propose a quantum metrology protocol for the localization of noncooperative pointlike target in three-dimensional space, by illuminating it with electromagnetic waves. It employs all spatial degrees freedom N entangled photons to achieve an uncertainty that is sqrt[N] times smaller each direction than what could be achieved N-independent or classical light same average intensity.

Following the rising interest in quantum information science, extension of a heat engine to regime by exploring microscopic systems has seen boon last decade. Although coherence system working medium been investigated play nontrivial role, complete understanding intrinsic advantage engines remains elusive. We experimentally demonstrate that correlation between and thermal bath is critical for Szilárd engine, where naturally excluded. By quantifying nonclassical through steering, we reveal...

Nonclassical correlations can be regarded as resources for quantum information processing. However, the classification problem of nonclassical states remains a challenge, even finite-size systems. Although there exists set criteria determining individual correlations, unified framework that is capable simultaneously classifying multiple still missing. In this Letter, we experimentally explored possibility applying machine-learning methods identifying correlations. Specifically, by using...

Nonlocality sharing for a three-qubit system via multilateral sequential measurements was deeply discussed. based on the multiple violations of Mermin-Ardehali-Belinskii-Klyshko (MABK) inequality in trilateral scenario can be observed, where all eight MABK inequalities violated simultaneously. Nevertheless, genuine nonlocality violation Svetlichny only observed unilateral scenario. Compared with two-qubit cases, shows more fruitful characteristics.

Abstract Recently quantum nonlocality has been classified into three distinct types: entanglement, Einstein-Podolsky-Rosen steering, and Bell’s nonlocality. Among which, is the strongest type. for states usually detected by violation of some inequalities, such as Clause-Horne-Shimony-Holt inequality two qubits. Steering a manifestation intermediate between entanglement This peculiar feature led to curious phenomenon, one-way steering. The steering was an important open question presented in...

Quantum steering is an important nonclassical resource for quantum information processing. However, even though lots of criteria exist, it still very difficult to efficiently determine whether arbitrary two-qubit state shared by Alice and Bob steerable or not, because the optimal measurement directions are unknown. In this work, we provide efficient detection scheme with help machine learning, where only need measure in a few fixed directions. order prove validity method, first realize...

Quantum network correlations have attracted strong interest because they may reveal new types of locality violations. Here we investigated nonlocality sharing in the extended bilocal scenario via weak measurements, which adds one more observer to either end well-known entanglement-swapping scenario. Intriguingly, can be revealed from multiple violation Branciard-Rosset-Gisin-Pironio inequality by considering two contrasting motivations intermediate observers, has no counterpart standard Bell...

Entanglement, quantum steering and nonlocality are distinct correlations which the resources behind various of information computation applications. However, a central question determining precise quantitative relation among them is still unresolved. Here, we present mapping criterion between Bell in bipartite qudit-qubit system, as well entanglement qubit-qudit starting from fundamental concepts correlations. Precise criteria derived analytically. Such independent form state. In particular,...

A well-known property of quantum nonlocality is monogamy. However, recent research by Silva et al. shows that multiple observers can share the using weak measurements [Phys. Rev. Lett. 114, 250401 (2015)]. In this paper, we deeply discuss sharing for an arbitrary two-qubit state via measurements. Two types sharing, passive and active which another type double violation Clauser-Horne-Shimony-Holt (CHSH) inequality with many counterintuitive results existing, are fully analyzed. The two quite...

Abstract The investigation of network nonlocality (NN) has expanded the study quantum nonlocality, yet it fails to fully capture complexities within networks. Recently, a stronger and more genuine definition NN, known as full (FNN), been explored, which is considered vital resource for realizing network-based device-independent cryptography protocols. In this work, we explore recycling FNN resources by analyzing sharing between different combinations observers. in an extended bilocal...

We propose a multiparty quantum clock synchronization protocol that makes optimal use of the maximal multipartite entanglement GHZ-type states. To realize protocol, different versions maximally entangled eigenstates collective energy are generated by local transformations distinguish among groupings parties. The sensitivity states to time differences between clocks can then be accessed if all parties share results their time-dependent measurements. efficiency is evaluated in terms...

We proposed and analyzed a scheme of precisely measuring orbital angular momentum (OAM) the vortex beams with help weak measurement process. The information $l$ unknown OAM state can be obtained by its spatial displacements. valid condition was completely discussed. Interestingly, it is shown that using two-dimensional displacements jointly very useful for large $l$. signal-to-noise ratio enhanced increasing weak-coupling $\ensuremath{\gamma}$ linearly as still satisfied. For fixed...

Detecting the entanglement structure, such as intactness and depth, of an n-qubit state is important for understanding imperfectness preparation in experiments. However, identifying structure usually requires exponential number local measurements. In this letter, we propose efficient machine learning based approach predicting depth simultaneously. The generalization ability classifier has been convincingly proved, it can precisely distinguish whole range pure generalized GHZ states which...

We aim to explore the scenario that a single Alice steers multiple Bobs by using weak measurements. The violations of two different Einstein-Podolsky-Rosen steering inequalities were discussed. Based on unbiased inputs, can steer when double violation Clauser-Horne-Shimony-Holt-like inequality is realized. Meanwhile, three be steered triple three-settings linear observed. More importantly, we theoretically inferred analytical formula maximal for corresponding inequality, which applied an...

We propose a scheme for the sharing of quantum steering among three observers, Alice, Bob, and Charlie, using standard projective measurements. show that in unilateral sequential scenario, Alice can steer Bob's Charlie's states conversely, Bob Charlie Alice's state. Unlike achieved through weak measurements, we use measurements to enable sharing. Quantum is demonstrated by violations linear inequality different observer combinations. find simultaneously both states, state, regardless whether...

Abstract With the rapid growth of controllable qubits in recent years, experimental multipartite entangled states can be created with high fidelity various moderate‐ and large‐scale physical systems. However, characterization entanglement structure remains a formidable challenge, as traditionally it requires exponential number local measurements to realize identification. Machine learning is demonstrated an efficient tool detect underlying for ideal states, but has non‐negligible...

We theoretically propose and experimentally demonstrate a modulated weak measurement scheme that permits precise estimation of the extended phase shift. By choosing frequency total post-selected light intensity as input output meter variables, respectively, linear model is established especially applicable to estimation. performing time-delay-dependent modulation strategy based on feedback experimental outcome, both high phase-sensitivity precision can be retained. have achieved at order...

Multiparticle interference is a fundamental phenomenon in the study of quantum mechanics. It was discovered recent experiment [Y.-S. Ra et al., Proc. Natl. Acad. Sci. USA 110, 1227 (2013)] that spectrally uncorrelated biphotons exhibited nonmonotonic quantum-to-classical transition four-photon Hong-Ou-Mandel (HOM) interference. In this work, we consider same scheme with correlated photons. By theoretical calculation and numerical simulation, found not only can be negatively or biphotons, but...

Efficient, reliable determination of a system's state is at the heart quantum science. Directly measuring any desired density-matrix elements unique challenge for both theorists and experimentalists, as standard methods have always suffered from rapid increase in complexity measurements reconstruction algorithms. This study presents an efficient scheme directly arbitrary density matrices with only one strong measurement, or weak each qudit. method important characterizing large-scale...

We propose a scheme called the weak measurement with two pointers to measure time delays in large dynamic range high precision. One pointer light frequency and other postselected probability play complementary role of time-delay estimation. By inserting main systematic errors, we study antierror capability amplification behavior types pointers, where shows stronger robustness against errors larger working general. The proof-of-principle experiments together Fisher information metric analysis...

Abstract Quatum nonlocality as a valuable resource is of vital importance in quantum information processing. The characterization the has been extensively investigated mainly for pure states, while relatively less know mixed states. Here we prove existence optimal GHZ paradox by using novel and simple method to extract an state that can saturate tradeoff relation between purity. In this paradox, logical inequality which formulated GHZ-typed event probabilities be violated maximally any fixed...

A single photon prepared in a time-energy state described by frequency comb combines the extreme precision of energy defined tooth with high sensitivity to small shifts time narrowness pulse long sequence pulses that describe frequency-comb domain. We show how this simultaneous suppression and uncertainties can be separation scales, we compare two-particle correlations an entangled state. To illustrate states frequency, consider Hong-Ou-Mandel dips observed two-photon interference when both...

To fully utilize the energy-time degree of freedom photons for optical quantum information processes, it is necessary to control and characterize states at extremely short time scales. For measurements beyond resolution available detectors, two-photon interference with a photon in reference pulse may be viable alternative. In this paper, we derive temporal measurement operators bunching statistics single input state photon. It shown that effects shape can expressed terms spectral filter...