The quantum state of a laser field

2002 ◽  
Vol 2 (2) ◽  
pp. 151-165
Author(s):  
S.J. van Enk ◽  
C.A. Fuchs
Keyword(s):  
Quantum State ◽  
Laser Field ◽  
Quantum Teleportation ◽  
Continuous Wave ◽  
Continuous Variable ◽  
Continuous Variables ◽  
Laser Fields ◽  
Information Theoretic ◽  
Quantum Optical ◽  
Theoretic Description

Optical implementations of quantum communication protocols typically involve laser fields. However, the standard description of the quantum state of a laser field is surprisingly insufficient to understand the quantum nature of such implementations. In this paper, we give a quantum information-theoretic description of a propagating continuous-wave laser field and reinterpret various quantum-optical experiments in light of this. A timely example is found in a recent controversy about the quantum teleportation of continuous variables. We show that contrary to the claims of T. Rudolph and B.C. Sanders [Phys. Rev. Lett. {\bf 87}, 077903 (2001)], a conventional laser can be used for quantum teleportation with continuous variables and for generating continuous-variable quantum entanglement. Furthermore, we show that optical coherent states do play a privileged role in the description of propagating laser fields even though they cannot be ascribed such a role for the intracavity field.

scholarly journals Deterministic quantum teleportation through fiber channels

2018 ◽  
Vol 4 (10) ◽  
pp. eaas9401 ◽  
Author(s):  
Meiru Huo ◽  
Jiliang Qin ◽  
Jialin Cheng ◽  
Zhihui Yan ◽  
Zhongzhong Qin ◽  
...  
Keyword(s):  
Communication Networks ◽  
Quantum State ◽  
Optical Fibers ◽  
Quantum Teleportation ◽  
Continuous Variable ◽  
Entangled State ◽  
Optical Modes ◽  
Unknown Quantum State ◽  
Einstein Podolsky Rosen ◽  
Fiber Channels

Quantum teleportation, which is the transfer of an unknown quantum state from one station to another over a certain distance with the help of nonlocal entanglement shared by a sender and a receiver, has been widely used as a fundamental element in quantum communication and quantum computation. Optical fibers are crucial information channels, but teleportation of continuous variable optical modes through fibers has not been realized so far. Here, we experimentally demonstrate deterministic quantum teleportation of an optical coherent state through fiber channels. Two sub-modes of an Einstein-Podolsky-Rosen entangled state are distributed to a sender and a receiver through a 3.0-km fiber, which acts as a quantum resource. The deterministic teleportation of optical modes over a fiber channel of 6.0 km is realized. A fidelity of 0.62 ± 0.03 is achieved for the retrieved quantum state, which breaks through the classical limit of1/2. Our work provides a feasible scheme to implement deterministic quantum teleportation in communication networks.

scholarly journals Quantum-Optical Spectrometry in Relativistic Laser–Plasma Interactions Using the High-Harmonic Generation Process: A Proposal

Photonics ◽  
2021 ◽  
Vol 8 (6) ◽  
pp. 192
Author(s):  
Theocharis Lamprou ◽  
Rodrigo Lopez-Martens ◽  
Stefan Haessler ◽  
Ioannis Liontos ◽  
Subhendu Kahaly ◽  
...  
Keyword(s):  
Harmonic Generation ◽  
Quantum Electrodynamics ◽  
Laser Field ◽  
High Harmonic ◽  
Intense Laser ◽  
Strong Laser Field ◽  
Laser Plasma Interactions ◽  
Strong Laser ◽  
Optical Spectrometry ◽  
Quantum Optical

Quantum-optical spectrometry is a recently developed shot-to-shot photon correlation-based method, namely using a quantum spectrometer (QS), that has been used to reveal the quantum optical nature of intense laser–matter interactions and connect the research domains of quantum optics (QO) and strong laser-field physics (SLFP). The method provides the probability of absorbing photons from a driving laser field towards the generation of a strong laser–field interaction product, such as high-order harmonics. In this case, the harmonic spectrum is reflected in the photon number distribution of the infrared (IR) driving field after its interaction with the high harmonic generation medium. The method was implemented in non-relativistic interactions using high harmonics produced by the interaction of strong laser pulses with atoms and semiconductors. Very recently, it was used for the generation of non-classical light states in intense laser–atom interaction, building the basis for studies of quantum electrodynamics in strong laser-field physics and the development of a new class of non-classical light sources for applications in quantum technology. Here, after a brief introduction of the QS method, we will discuss how the QS can be applied in relativistic laser–plasma interactions and become the driving factor for initiating investigations on relativistic quantum electrodynamics.

scholarly journals Protocol for optically pumping AlH+ to a pure quantum state

2020 ◽  
Vol 22 (42) ◽  
pp. 24423-24430
Author(s):  
Panpan Huang ◽  
Schuyler Kain ◽  
Antonio G. S. de Oliveira-Filho ◽  
Brian C. Odom
Keyword(s):  
Quantum State ◽  
Laser Fields ◽  
Pure Quantum State ◽  
Hyperfine State

Three laser fields drive the population of AlH+ to a single hyperfine state.

Entanglement and nonlocality for a mixture of a pair-coherent state

2003 ◽  
Vol 3 (2) ◽  
pp. 106-115
Author(s):  
S. Mancini ◽  
P. Tombesi
Keyword(s):  
Coherent State ◽  
Quantum Teleportation ◽  
Single Photon ◽  
Continuous Variables ◽  
Bell’S Inequalities ◽  
Nonclassical Properties ◽  
Pair Coherent State ◽  
Photon Loss ◽  
Phase Randomization ◽  
Degree Of Entanglement

We consider a bipartite continuous variables quantum mixture coming from phase randomization of a pair-coherent state. We study the nonclassical properties of such a mixture. In particular, we quantify its degree of entanglement, then we show possible violations of Bell's inequalities. We also consider the use of this mixture in quantum teleportation. Finally, we compare this mixture with that obtained from a pair-coherent state by single photon loss.

On the classical character of control fields in quantum information processing

2002 ◽  
Vol 2 (1) ◽  
pp. 1-13
Author(s):  
S.J. van Enk ◽  
H.J. Kimble
Keyword(s):  
Quantum Computing ◽  
Information Processing ◽  
Quantum Information ◽  
Laser Beam ◽  
Quantum State ◽  
Quantum Communication ◽  
Quantum Information Processing ◽  
Laser Fields ◽  
Undesirable Property

Control fields in quantum information processing are almost by definition assumed to be classical. In reality, however, when such a field is used to manipulate the quantum state of qubits, the qubits always become slightly entangled with the field. For quantum information processing this is an undesirable property, as it precludes perfect quantum computing and quantum communication. Here we consider the interaction of atomic qubits with laser fields and quantify atom-field entanglement in various cases of interest. We find that the entanglement decreases with the average number of photons \bar{n} in a laser beam as $E\propto\log_2 \bar{n}/\bar{n}$ for $\bar{n}\rightarrow\infty$.

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