scholarly journals Experimental localisation of quantum entanglement through monitored classical mediator

Quantum ◽  
2021 ◽  
Vol 5 ◽  
pp. 478
Author(s):  
Soham Pal ◽  
Priya Batra ◽  
Tanjung Krisnanda ◽  
Tomasz Paterek ◽  
T. S. Mahesh
Keyword(s):  
Quantum Entanglement ◽  
Quantum Coherence ◽  
Figure Of Merit ◽  
Optimal Growth ◽  
Quantum Correlations ◽  
Initial State ◽  
Classical Communication ◽  
Classical State ◽  
Quantum Particles ◽  
Quantum Optomechanics

Quantum entanglement is a form of correlation between quantum particles that cannot be increased via local operations and classical communication. It has therefore been proposed that an increment of quantum entanglement between probes that are interacting solely via a mediator implies non-classicality of the mediator. Indeed, under certain assumptions regarding the initial state, entanglement gain between the probes indicates quantum coherence in the mediator. Going beyond such assumptions, there exist other initial states which produce entanglement between the probes via only local interactions with a classical mediator. In this process the initial entanglement between any probe and the rest of the system "flows through" the classical mediator and gets localised between the probes. Here we theoretically characterise maximal entanglement gain via classical mediator and experimentally demonstrate, using liquid-state NMR spectroscopy, the optimal growth of quantum correlations between two nuclear spin qubits interacting through a mediator qubit in a classical state. We additionally monitor, i.e., dephase, the mediator in order to emphasise its classical character. Our results indicate the necessity of verifying features of the initial state if entanglement gain between the probes is used as a figure of merit for witnessing non-classical mediator. Such methods were proposed to have exemplary applications in quantum optomechanics, quantum biology and quantum gravity.

scholarly journals Quantum Information in Neural Systems

Symmetry ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 773
Author(s):  
Danko D. Georgiev
Keyword(s):  
Quantum Entanglement ◽  
Quantum Coherence ◽  
Quantum Physics ◽  
Quantitative Measure ◽  
Quantum States ◽  
Quantum Evolution ◽  
Einstein Relation ◽  
Schmidt Decomposition ◽  
The Central Nervous System ◽  
The Individual

Identifying the physiological processes in the central nervous system that underlie our conscious experiences has been at the forefront of cognitive neuroscience. While the principles of classical physics were long found to be unaccommodating for a causally effective consciousness, the inherent indeterminism of quantum physics, together with its characteristic dichotomy between quantum states and quantum observables, provides a fertile ground for the physical modeling of consciousness. Here, we utilize the Schrödinger equation, together with the Planck–Einstein relation between energy and frequency, in order to determine the appropriate quantum dynamical timescale of conscious processes. Furthermore, with the help of a simple two-qubit toy model we illustrate the importance of non-zero interaction Hamiltonian for the generation of quantum entanglement and manifestation of observable correlations between different measurement outcomes. Employing a quantitative measure of entanglement based on Schmidt decomposition, we show that quantum evolution governed only by internal Hamiltonians for the individual quantum subsystems preserves quantum coherence of separable initial quantum states, but eliminates the possibility of any interaction and quantum entanglement. The presence of non-zero interaction Hamiltonian, however, allows for decoherence of the individual quantum subsystems along with their mutual interaction and quantum entanglement. The presented results show that quantum coherence of individual subsystems cannot be used for cognitive binding because it is a physical mechanism that leads to separability and non-interaction. In contrast, quantum interactions with their associated decoherence of individual subsystems are instrumental for dynamical changes in the quantum entanglement of the composite quantum state vector and manifested correlations of different observable outcomes. Thus, fast decoherence timescales could assist cognitive binding through quantum entanglement across extensive neural networks in the brain cortex.

scholarly journals Can Quantum Correlations Lead to Violation of the Second Law of Thermodynamics?

Entropy ◽  
2021 ◽  
Vol 23 (5) ◽  
pp. 573
Author(s):  
Alexey V. Melkikh
Keyword(s):  
Quantum Entanglement ◽  
Local Equilibrium ◽  
Heat Engine ◽  
Thermodynamic Quantity ◽  
Second Law Of Thermodynamics ◽  
Quantum Correlations ◽  
Von Neumann Entropy ◽  
Second Law ◽  
Carnot Cycle ◽  
Technical Discussion

Quantum entanglement can cause the efficiency of a heat engine to be greater than the efficiency of the Carnot cycle. However, this does not mean a violation of the second law of thermodynamics, since there is no local equilibrium for pure quantum states, and, in the absence of local equilibrium, thermodynamics cannot be formulated correctly. Von Neumann entropy is not a thermodynamic quantity, although it can characterize the ordering of a system. In the case of the entanglement of the particles of the system with the environment, the concept of an isolated system should be refined. In any case, quantum correlations cannot lead to a violation of the second law of thermodynamics in any of its formulations. This article is devoted to a technical discussion of the expected results on the role of quantum entanglement in thermodynamics.

scholarly journals FROZEN DISCORD IN NON-MARKOVIAN DEPHASING CHANNELS

2011 ◽  
Vol 09 (03) ◽  
pp. 981-991 ◽  
Author(s):  
LAURA MAZZOLA ◽  
JYRKI PIILO ◽  
SABRINA MANISCALCO
Keyword(s):  
Hilbert Space ◽  
Colored Noise ◽  
Geometric Interpretation ◽  
Quantum Decoherence ◽  
Initial State ◽  
Memory Kernel ◽  
Single Qubit ◽  
Classical State ◽  
Classical Correlations ◽  
Quantum And Classical Correlations

We investigate the dynamics of quantum and classical correlations in a system of two qubits under local colored-noise dephasing channels. The time evolution of a single qubit interacting with its own environment is described by a memory kernel non-Markovian master equation. The memory effects of the non-Markovian reservoirs introduce new features in the dynamics of quantum and classical correlations compared to the white noise Markovian case. Depending on the geometry of the initial state, the system can exhibit frozen discord and multiple sudden transitions between classical and quantum decoherence [L. Mazzola, J. Piilo and S. Maniscalco, Phys. Rev. Lett. 104 (2010) 200401]. We provide a geometric interpretation of those phenomena in terms of the distance of the state under investigation to its closest classical state in the Hilbert space of the system.

The impact of resource on remote quantum correlation Preparation

2015 ◽  
Vol 15 (13&14) ◽  
pp. 1223-1232
Author(s):  
Chengjun Wu ◽  
Bin Luo ◽  
Hong Guo
Keyword(s):  
Quantum Entanglement ◽  
Quantum Correlation ◽  
Quantum Discord ◽  
Entangled States ◽  
Shared Resources ◽  
Classical Communication ◽  
Bell Measurement ◽  
Measurement Results ◽  
The Impact

When Alice and Bob share two pairs of quantum correlated states, Alice can remotely prepare quantum entanglement and quantum discord in Bob’s side by measuring the parts in her side and telling Bob the measurement results by classical communication. For remote entanglement preparation, entanglement is necessary . We find that for some shared resources having the same amount of entanglement, when Bell measurement is used, the entanglement remotely prepared can be different, and more discord in the resources actually decreases the entanglement prepared. We also find that for some resources with more entanglement, the entanglement remotely prepared may be less. Therefore, we conclude that entanglement is a necessary resource but may not be the only resource responsible for the entanglement remotely prepared, and discord does not likely to assist this process. Also, for the preparation of discord, we find that some states with no entanglement could outperform entangled states.

scholarly journals Cost of Exactly Simulating Quantum Entanglement with Classical Communication

1999 ◽  
Vol 83 (9) ◽  
pp. 1874-1877 ◽  
Author(s):  
Gilles Brassard ◽  
Richard Cleve ◽  
Alain Tapp
Keyword(s):  
Quantum Entanglement ◽  
Classical Communication

scholarly journals Resonant tunneling in natural photosynthetic systems

2021 ◽  
Author(s):  
Kit M Gerodias ◽  
Maria Victoria Carpio Bernido ◽  
Christopher Casenas Bernido
Keyword(s):  
Numerical Simulations ◽  
Effective Mass ◽  
Quantum Entanglement ◽  
Resonant Tunneling ◽  
Quantum Coherence ◽  
Geometrical Structure ◽  
Higher Plants ◽  
Internal Quantum Efficiency ◽  
Transmission Coefficients ◽  
Outstanding Problem

Abstract The high internal quantum efficiency observed in higher plants remains an outstanding problem in understanding photosynthesis. Several approaches such as quantum entanglement and quantum coherence have been explored. However, none has yet drawn an analogy between superlattices and the geometrical structure of granal thylakoids in leaves. In this paper, we calculate the transmission coefficients and perform numerical simulations using the parameters relevant to a stack of thylakoid discs. We then show that quantum resonant tunneling can occur at low effective mass of particles for 680 nm and 700 nm incident wavelengths corresponding to energies at which photosynthesis occurs.

scholarly journals Local quantum uncertainty as a robust metric to characterize discord-like quantum correlations in subsets of the chromophores in photosynthetic light-harvesting complexes

2020 ◽  
Vol 66 (4 Jul-Aug) ◽  
pp. 525
Author(s):  
M. Chávez-Huerta ◽  
F. Rojas
Keyword(s):  
Quantum Coherence ◽  
Light Harvesting ◽  
Green Sulfur Bacteria ◽  
Quantum Correlations ◽  
Light Harvesting Complexes ◽  
Thermal Equilibrium State ◽  
Light Harvesting Complex ◽  
Quantum Uncertainty ◽  
Local Quantum Uncertainty ◽  
Local Quantum

Green sulfur bacteria is a photosynthetic organism whose light-harvesting complex accommodates a pigment-protein complex called Fenna-Matthews-Olson (FMO). The FMO complex sustains quantum coherence and quantum correlations between the electronic states of spatially separated pigment molecules as energy moves with nearly a 100% quantum efficiency to the reaction center. We present a method based on the quantum uncertainty associated to local measurements to quantify discord-like quantum correlations between two subsystems where one is a qubit and the other is a qudit. We implement the method by calculating local quantum uncertainty (LQU), concurrence, and coherence between subsystems of pure and mixed states represented by the eigenstates and by the thermal equilibrium state determined by the FMO Hamiltonian. Three partitions of the seven chromophores network define the subsystems: one chromophore with six chromophores, pairs of chromophores, and one chromophore with two chromophores. Implementation of the LQU approach allows us to characterize quantum correlations that had not been studied before, identify the most quantum correlated subsets of chromophores, and determine that, in the strongest associations of chromophores, the LQU is a monotonically increasing function of the coherence.

scholarly journals Complementary relation of quantum coherence and quantum correlations in multiple measurements

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Zeyang Fan ◽  
Yi Peng ◽  
Yu-Ran Zhang ◽  
Shang Liu ◽  
Liang-Zhu Mu ◽  
...  
Keyword(s):  
Quantum Coherence ◽  
Quantum Correlations ◽  
Complementary Relation ◽  
Multiple Measurements

More on extracting information about the initial state from the black hole radiation

2018 ◽  
Vol 33 (19) ◽  
pp. 1850108
Author(s):  
Hossein Ghaforyan ◽  
Somayyeh Shoorvazi ◽  
Alireza Sepehri ◽  
Tooraj Ghaffary
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Density Matrix ◽  
Quantum Entanglement ◽  
Event Horizon ◽  
Initial State ◽  
Black Hole Radiation ◽  
Total Information ◽  
Quantum Treatment ◽  
Collapse Process

Recently, some authors showed that a classical collapse scenario ignores this richness of information in the resulting spectrum and a consistent quantum treatment of the entire collapse process might allow us to retrieve much more information from the spectrum of the final radiation. We confirm these results and show that by considering the quantum entanglement between metrics, we can uncover information of black holes. In our model, a density matrix is defined for the spaces, both inside and outside of the event horizon. These inside and outside spaces of black holes are obtained by tracing from a bigger space. An observer that lives in this big space can recover total information regarding the inside and outside of black hole.

Steady-state quantum correlation measurement in hybrid optomechanical systems

2020 ◽  
pp. 2050046
Author(s):  
Tesfay Gebremariam Tesfahannes ◽  
Merkebu Dereje Getahune
Keyword(s):  
Correlation Function ◽  
Steady State ◽  
Quantum Entanglement ◽  
Quantum Correlation ◽  
Optical Cavity ◽  
Quantum Correlations ◽  
Correlation Measurement ◽  
Atomic Ensemble ◽  
Optomechanical System ◽  
Optomechanical Systems

In this paper, we investigate the steady-state of quantum correlation measurement of hybrid optomechanical systems. The first system consists of a single optomechanical system simultaneously coupled to a mechanical oscillator. While the second system is a hybrid optomechanical system consisting of an atomic ensemble placed in between the optical cavity and mirror. For both optomechanical systems, we formulate the Hamiltonian and the explicit expression of the covariance matrix leading to the dynamic of the system. Under the linearization approximation, we investigate the steady-state quantum correlations which are quantified through the correlation function of non-Hermitian operators, while the logarithmic negativity is used to quantify the amount of quantum entanglement between the subsystems. Furthermore, our proposed quantum correlation function can be used to quantify the entangled bipartite states that are correlative and transfer information. It is found that the transfer of quantum correlations between the subsystem is related to the detuning and coupling strength. Our results provide a realistic route toward remote quantum entanglement detection and a framework of future realistic fiber-optic quantum network operating applications.

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