Quantum non-demolition measurements in optics and quantum optical repeaters

AbstractUnder nonequilibrium conditions, quantum optical systems reveal unusual properties that might be distinct from those in condensed matter. The fundamental reason is that photonic eigenstates can have arbitrary occupation numbers, whereas in electronic systems these are limited by the Pauli principle. Here, we address the steady-state transport of pseudothermal photons between two waveguides connected through a cavity with Bose–Hubbard interaction between photons. One of the waveguides is subjected to a broadband incoherent pumping. We predict a continuous transition between the regimes of Lorentzian and Gaussian chaotic light emitted by the cavity. The rich variety of nonequilibrium transport regimes is revealed by the zero-frequency noise. There are three limiting cases, in which the noise-current relation is characterized by a power-law, $$S\propto J^\gamma$$ S ∝ J γ . The Lorentzian light corresponds to Breit-Wigner-like transmission and $$\gamma =2$$ γ = 2 . The Gaussian regime corresponds to many-body transport with the shot noise ($$\gamma =1$$ γ = 1 ) at large currents; at low currents, however, we find an unconventional exponent $$\gamma =3/2$$ γ = 3 / 2 indicating a nontrivial interplay between multi-photon transitions and incoherent pumping. The nonperturbative solution for photon dephasing is obtained in the framework of the Keldysh field theory and Caldeira-Leggett effective action. These findings might be relevant for experiments on photon blockade in superconducting qubits, thermal states transfer, and photon statistics probing.

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“Seeing Is Believing”—In-Depth Analysis by Co-Imaging of Periodically-Poled X-Cut Lithium Niobate Thin Films

Crystals ◽

10.3390/cryst11030288 ◽

2021 ◽

Vol 11 (3) ◽

pp. 288

Author(s):

Sven Reitzig ◽

Michael Rüsing ◽

Jie Zhao ◽

Benjamin Kirbus ◽

Shayan Mookherjea ◽

...

Keyword(s):

Lithium Niobate ◽

Second Harmonic ◽

Imaging Techniques ◽

Piezoresponse Force Microscopy ◽

Periodically Poled ◽

Near Surface ◽

Domain Structures ◽

Depth Analysis ◽

Improved Performance ◽

Quantum Optical

Nonlinear and quantum optical devices based on periodically-poled thin film lithium niobate (PP-TFLN) have gained considerable interest lately, due to their significantly improved performance as compared to their bulk counterparts. Nevertheless, performance parameters such as conversion efficiency, minimum pump power, and spectral bandwidth strongly depend on the quality of the domain structure in these PP-TFLN samples, e.g., their homogeneity and duty cycle, as well as on the overlap and penetration depth of domains with the waveguide mode. Hence, in order to propose improved fabrication protocols, a profound quality control of domain structures is needed that allows quantifying and thoroughly analyzing these parameters. In this paper, we propose to combine a set of nanometer-to-micrometer-scale imaging techniques, i.e., piezoresponse force microscopy (PFM), second-harmonic generation (SHG), and Raman spectroscopy (RS), to access the relevant and crucial sample properties through cross-correlating these methods. Based on our findings, we designate SHG to be the best-suited standard imaging technique for this purpose, in particular when investigating the domain poling process in x-cut TFLNs. While PFM is excellently recommended for near-surface high-resolution imaging, RS provides thorough insights into stress and/or defect distributions, as associated with these domain structures. In this context, our work here indicates unexpectedly large signs for internal fields occurring in x-cut PP-TFLNs that are substantially larger as compared to previous observations in bulk LN.

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Light Amplification by Quantum Confinement (LAQC) in quantum optical lithography

Optics & Laser Technology ◽

10.1016/j.optlastec.2021.107287 ◽

2021 ◽

Vol 143 ◽

pp. 107287

Author(s):

Eugen Pavel

Keyword(s):

Quantum Confinement ◽

Optical Lithography ◽

Light Amplification ◽

Quantum Optical

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Continuous-variable Clauser-Horne Bell-type inequality: A tool to unearth the nonlocality of continuous-variable quantum-optical systems

Physical Review A ◽

10.1103/physreva.103.042224 ◽

2021 ◽

Vol 103 (4) ◽

Author(s):

Chandan Kumar ◽

Gaurav Saxena ◽

Arvind

Keyword(s):

Type Inequality ◽

Continuous Variable ◽

Optical Systems ◽

Quantum Optical

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

Photonics ◽

10.3390/photonics8060192 ◽

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.

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