Degenerate Optical Parametric Amplifier Research Articles

Tunable multicolor optomechanically induced transparency and slow-fast light in hybrid electro-optomechanical system

Abstract We investigate the tunable multicolor optomechanically induced transparency and the effect of slow/fast light in a hybrid electro-optomechanical system, in which a degenerate optical parametric amplifier (OPA) and a Λ − type three-level atomic ensemble are placed in a optical cavity with two oscillator modes. The system is driven by a strong pump field and a weak probe field, respectively. Multicolor transparency windows appear in the output field under the atom-photon-OPA-phonon-phonon coherent interaction. And the position and width of the transparent port of the output field can be manipulated by properly modifying the different parameters of the subsystem. We also research the slow/fast light effect related to phase and group delay in the probe field. Our proposal provides a great flexibility for phonon storage and has some potential applications in quantum information processing.

Improving the Stationary Entanglement of a Laguerre-Gaussian Cavity Mode with a Rotating Mirror via Nonlinear Cross-Kerr Interactions and Parametric Interactions.

Quantum entanglement is essential in performing many quantum information tasks. Here, we theoretically investigate the stationary entanglement between a Laguerre-Gaussian (LG) cavity field and a rotating end mirror in an LG-cavity optorotational system with a nonlinear cross-Kerr (CK) interaction and a degenerate optical parametric amplifier (OPA). We calculate the logarithmic negativity of the system to quantify the stationary entanglement. We examine the influence of various system parameters such as the cavity detuning, the strength of the nonlinear CK interaction, the parametric gain and phase of the OPA, the power of the input Gaussian laser, the topological charge of the LG-cavity field, the mass of the rotating end mirror, and the ambient temperature on the stationary entanglement. Under the combined effect of the nonlinear CK interaction and the OPA, we find that the stationary entanglement can be substantially enhanced at lower Gaussian laser powers, smaller topological charges of the LG-cavity field, and larger masses of the rotating end mirror. We show that the combination of the nonlinear CK interaction and the OPA can make the stationary entanglement more robust against the ambient temperature.

Frequency‐Division Multiplexing Continuous Variable Quantum Dense Coding with Broadband Entanglement

AbstractQuantum dense coding (QDC) provides great potential for high‐capacity quantum communication. However, it is highly demanded for practical applications to realize high‐capacity QDC with multiple coded information. Here, a high‐capacity QDC with multiple streams is reported in different channels simultaneously through frequency‐division multiplexing (FDM). The broadband entangled state is generated from a pair of degenerate optic al parametric amplifiers with short cavity lengths. Based on the resultant broadband entanglement, multiple pieces of information coded using binary phase shift keying (BPSK) are transferred with the FDM method. As an experimental demonstration, four pieces of information composed of pseudo‐random numbers are transmitted at a rate of 4 Mbit s–1 using BPSK encoding. The decoded bit error rate reaches , which is an average 35‐fold improvement compared with the classical scheme. Furthermore, it is possible to make full use of sideband resource for four different information by using orthogonal FDM. This scheme can be extended to more different information by directly increasing the FDM sideband subchannels, and opens an avenue to construct high‐capacity quantum communication, while minimizing the cost of quantum resource.

Weak Force Sensing Based on Optical Parametric Amplification in a Cavity Optomechanical System Coupled in Series with Two Oscillators

AbstractIn the realm weak force sensing, an important issue is to suppress fundamental noise (quantum noise and thermal noise), as they limit the accuracy of force measurement. In this study, a weak force sensing scheme that combines a degenerate optical parametric amplifier (OPA) and an auxiliary mechanical oscillator into a cavity optomechanical system to reduce quantum noise is investigated. It is demonstrated that the noise reduction of two coupled oscillators depends on their norm mode splitting. and provide a classic analogy and quantum perspective for further clarification. Besides, the noise reduction mechanism of OPA is to reduce the fluctuation of photon number and enhance the squeezing of the cavity field. A specific design is proposed that aimed at enhancing the joint effect of both, beyond what can be achieved using OPA alone or two series coupled oscillators. This scheme provides a new perspective for deeper understanding of cavity field squeezing and auxiliary oscillator in force sensing.

Steady-state entanglement in a hybrid optomechanical system enhanced by optical parametric amplifiers

In this paper, we investigate the degree of steady-state entanglement using a hybrid optomechanical system, where the separate cavities contain a degenerate optical parametric amplifier (DOPA). Particularly, under the linearization approximation, the steady-state entanglement is quantified through logarithmic negativity. The bipartite entanglement between cavity-mechanical oscillator modes and two cavity modes is analyzed through the applicable choice of nonlinear gain of OPA, optical cavity detuning, and cavity-cavity coupling strength. It is found that the steady-state entanglement increases with the nonlinear gain of OPA medium and normalized detuning. We further emphasize the influence of cavity-cavity coupling parameter on the bipartite entanglement, and the generation of entanglement can be transferred entirely due to the coupling strengths. The main contribution of coupling parameters on the entanglement of the two modes of mechanical oscillators significantly altered and increased. The observed possibility of transferring the emerging entanglement of the states of light in the two cavities to the modes of the accompanying mechanical oscillators is expected to be a valuable asset in the practical realization of quantum information processing.

Sub-8-fs pulses in the visible to near-infrared by a degenerate optical parametric amplifier.

This work presents a single-stage optical parametric amplifier (OPA) operating at degeneracy (DOPA) and pumped by the third harmonic of a Yb:KGW laser system. This DOPA exploits the broad amplification bandwidth that occurs with type-I phase-matching in β-barium borate (BBO) when signal and idler overlap in the spectrum. The output pulses span from 590 to 780 nm (1.59-2.10 eV) with 7.75-fs duration after compression. Ultrashort pulses with similar bandwidths in this spectral window complement the existing array of optical parametric amplifiers that cover either the visible or the near-IR spectral regions with sub-10-fs pulses. This source of ultrashort optical pulses will enable the application of sophisticated spectroscopy techniques to the study of electronic coherences and energy migration pathways in biological, chemical, and condensed matter systems.

Enhanced Entanglement of the Two Cavity Modes in the Laguerre–Gaussian Cavity Optorotating System via an Optical Parametric Amplifier

Quantum entanglement in macroscopic systems plays an important role in quantum information processing. Here, we show that the steady-state entanglement between the two cavity modes in the macroscopic Laguerre–Gaussian (L–G) cavity optorotating system can be enhanced by placing a degenerate optical parametric amplifier (OPA) inside the cavity. The two L–G cavity modes are coupled to the same rotating mirror and are respectively driven at the red and blue mechanical sidebands. We use the logarithmic negativity to quantify the steady-state entanglement between the two cavity modes. We study the influences of the nonlinear gain and phase of the OPA, the temperature of the environment, and the angular momentums of the two cavity modes on the entanglement between the two cavity modes. In the cryogenic environment temperatures, when the angular momentums of the two cavity modes are identical, the enhancement of the entanglement between the two cavity modes by the OPA is the most significant.

Electromagnetically induced grating in a nonlinear optomechanical cavity

Abstract We investigate theoretically the Fraunhofer diffraction pattern of the output field in a nonlinear optomechanical cavity with a degenerate optical parametric amplifier (OPA) and a higher order excited atomic ensemble. Studies show that the higher-order-excitation atom, which is similar to the degenerate OPA that acts as a nonlinear medium, induces an electromagnetically induced grating in the output spectrum of the probe field. The coherence of the mechanical oscillator leads to transfer of the probe energy in different diffraction orders of the probe field spectrum such that the phenomenon of optomechanically induced grating is generated from the output probe field. In particular, the presence of nonlinearities with the degenerate OPA and the higher order excited atoms can significantly affect the efficiency of the diffraction pattern providing an additional flexibility for controlling optical properties.

Simultaneous Preparation of Two Optical Cat States Based on a Nondegenerate Optical Parametric Amplifier

AbstractThe cat state, known as the superposition of coherent states, has broad applications in quantum computation and quantum metrology. Increasing the number of optical cat states is crucial to implement complex quantum information tasks based on them. Here, two optical cat states are prepared simultaneously based on a nondegenerate optical parametric amplifier. By subtracting one photon from each of two squeezed vacuum states, two odd cat states with orthogonal superposition direction in phase space are prepared simultaneously, which have similar fidelity of 60% and amplitude of 1.2. Compared with the traditional method to generate two odd optical cat states based on two degenerate optical parametric amplifiers, only one nondegenerate optical parametric amplifier is applied in this experiment, which saves half of the quantum resources of nonlinear cavities. The presented results make a step toward preparing the four‐component cat state, which has potential applications in fault‐tolerant quantum computation.

Highly CEP-stable optical parametric amplifier at 2 µm with a few-cycle duration and 100 kHz repetition rate.

We develop a BiB3O6 (BiBO)-based optical parametric amplifier in the spectral region around 2 µm using a Yb:KGW amplifier operating at 100 kHz. The two-stage degenerate optical parametric amplification results in a typical output energy of 30 µJ after compression, spectrum covering 1.7-2.5 µm range, and a pulse duration fully compressible down to 16.4 fs, corresponding to 2.3 cycles. Due to the inline difference frequency generation of the seed pulses, the carrier envelope phase (CEP) is passively stabilized without feedback over 11 hours at the level below 100 mrad including a long-term drift. Short-term statistical analysis in the spectral domain further shows a behavior qualitatively different from that of parametric fluorescence, indicating high degree of suppression of optical parametric fluorescence. The high phase stability together with the few-cycle pulse duration is promising for the investigation of high-field phenomena such as subcycle spectroscopy in solids or high harmonics generation.

A Bright Squeezed Light Source for Quantum Sensing

The use of optical sensing for in vivo applications is compelling, since it offers the advantages of non-invasiveness, non-ionizing radiation, and real-time monitoring. However, the signal-to-noise ratio (SNR) of the optical signal deteriorates dramatically as the biological tissue increases. Although increasing laser power can improve the SNR, intense lasers can severely disturb biological processes and viability. Quantum sensing with bright squeezed light can make the measurement sensitivity break through the quantum noise limit under weak laser conditions. A bright squeezed light source is demonstrated to avoid the deterioration of SNR and biological damage, which integrates an external cavity frequency-doubled laser, a semi-monolithic standing cavity with periodically poled titanyl phosphate (PPKTP), and a balanced homodyne detector (BHD) assembled on a dedicated breadboard. With the rational design of the mechanical elements, the optical layout, and the feedback control equipment, a maximum non-classical noise reduction of −10.7 ± 0.2 dB is observed. The average squeeze of −10 ± 0.2 dB in continuous operation for 60 min is demonstrated. Finally, the intracavity loss of degenerate optical parametric amplifier (DOPA) and the initial bright squeezed light can be calculated to be 0.0021 and −15.5 ± 0.2 dB, respectively. Through the above experimental and theoretical analysis, the direction of improving bright squeeze level is pointed out.

Compact source for quadripartite deterministically entangled optical fields

Since entangled multiple optical fields were identified as the building blocks of quantum networks, the quadripartite entangled optical fields have been produced by using four degenerate optical parametric amplifiers or two nondegenerate optical parametric amplifiers (NOPAs). However, realizing an efficient and compact source for multiple quantum users has remained an outstanding challenge, hindering their practical applications. Here, we proposed a compact and feasible scheme to deterministically entangle four spatially separated optical fields, employing only a single NOPA. Accordingly, two-sided output NOPA-based optical fields were coupled on a beam splitter network to form the quadripartite entangled state, causing the deterministic generation of both the Greenberger–Horne–Zeilinger (GHZ) and the linear cluster states in this compact entanglement source. We also obtained the optimal experimental parameters based on the simulation results, thereby providing a direct reference for experimental implementation. Our findings propose that the resultant GHZ and linear cluster states can be potentially applied in quantum-enhanced information science, specifically in quantum secret sharing, controlled quantum teleportation networks, and quantum-entangled atomic ensemble networks.

Generation of Long-Term Stable Squeezed Vacuum States Using Dither-Locking Technique

We report the generation of long-term stable squeezed vacuum states at 1064 nm using a degenerate optical parametric amplifier (DOPA) with a periodically poled KTiOPO4 crystal (PPKTP). The OPA is pumped by a 532 nm light produced by frequency doubling the fundamental light with a bow-tie enhancement second harmonic generator (SHG). When the DOPA and relative phases are locked using a dither-locking method, the squeezed vacuum states are stably measured over 2 h at 11 MHz. The highly compact and simple squeezed light source is suitable for applications in quantum optics experiments.

Stationary Entanglement between Two Rotating Mirrors in a Laguerre–Gaussian Rotational‐Cavity Optomechanical System with an Optical Parametric Amplifier

AbstractGeneration of entanglement between macroscale mechanical oscillators is challenging yet important for future quantum technologies. Here, the possibility of creating a steady‐state entanglement between two rotating mirrors in a Laguerre–Gaussian (LG) rotational‐cavity optomechanical system by placing an especially tuned degenerate optical parametric amplifier (OPA) inside the cavity is theoretically explored. In the resolved‐sideband regime, a LG cavity mode is driven by a Gaussian laser beam tuned to the first lower mechanical sideband. The Duan quantity and the logarithmic negativity is used to study the stationary entanglement between two rotating mirrors. The influence of the parametric gain and phase of the OPA, the input laser power, the temperature of the environment, and the topological charge of the LG cavity mode on the mechanical entanglement are investigated. The achievable maximal degree of entanglement is limited by the parametric gain of the OPA.

Improving the Stochastic Feedback Cooling of a Mechanical Oscillator Using a Degenerate Parametric Amplifier

Cooling of a macroscopic mechanical resonator to extremely low temperatures is a necessary condition to observe a variety of macroscopic quantum phenomena. Here, we study the stochastic feedback cooling of a mechanical resonator in an optomechanical system with a degenerate optical parametric amplifier (OPA). In the bad-cavity limit, we find that the OPA can enhance the cooling of the movable mirror in the stochastic feedback cooling scheme. The movable mirror can be cooled from 132 mK to 0.033 mK, which is lower than that without the OPA by a factor of about 5.

Sub-three-cycle pulses at 2 µm from a degenerate optical parametric amplifier.

In this work we present a compact two-stage optical parametric amplifier (OPA) pumped at degeneracy by the fundamental of a Yb:KGW laser system. The output pulses span from 1.7 to 2.5 µm (120-176 THz) and are compressed to a sub-20 fs duration. This parametric amplifier exploits the broad phase-matching bandwidth at the degeneracy point in bismuth triborate (BiBO) and periodically poled lithium tantalate (PPLT). The result drastically expands the availability of ultrashort pulses with few-microjoule energy from near-infrared (NIR) to even longer wavelengths in the mid-infrared (MIR) spectral region.

Phase-sensitive manipulation of squeezed state by a degenerate optical parametric amplifier inside coupled optical resonators

Phase-sensitive manipulation of squeezed state by a degenerate optical parametric amplifier inside coupled optical resonators

Force sensing and cooling for the mechanical membrane in a hybrid optomechanical system

A study on force sensing and cooling for the mechanical membrane in a dissipative optomechanical system (OMS) with a degenerate optical parametric amplifier (OPA) and an optical Kerr medium is presented. The optimal phase angle can contribute to achieve much better force sensing than the case of the arbitrary phase angle. Specifically, at the blue detuning between the cavity field and the input laser the coexistence of the OPA and the Kerr medium plays an important role in improving the force sensitivity over the case of a bare OMS, while at the red detuning the bare OMS demonstrates more effective force sensitivity than the case of the coexistence of the OPA and the Kerr medium. The coexistence of the OPA and the Kerr medium is helpful to achieve more stable force sensitivity, which results from the change of the normalized cavity detuning having little effect on the force sensitivity of the system. In addition, for the existence of only nonlinear gain of the OPA, the study shows that at the blue detuning the temperature of the mechanical membrane can be achieved more effectively than in the case of the bare OMS, while at the red detuning, with increasing value of the nonlinear gain of the OPA, the cooling of the membrane is weakened. For the existence of the Kerr medium, at continuous detuning the effective temperature of the mechanical membrane is below the temperature of the environment. In quantum engineering, this scheme may have potential applications in precision measurement and quantum manipulation.

Cooling and thermophonon transports in nonlinear optomechanical systems

We propose theoretically a nonlinear optomechanical system with a suspended graphene sheet, a single atom and a degenerate optical parametric amplifier to explore the ground-state cooling of the graphene oscillator and the steady-state thermophonon flux flowing from the thermal bath of the graphene oscillator into the optomechanical system. We find that the cooling properties of the graphene oscillator and the magnitude of thermophonon flux can be controlled flexibly by changing the vacuum coupling strength between the trapped atom and the nearby graphene sheet. In particular, the maximum thermophonon flux always corresponds to the minimum effective phonon number of the graphene sheet, which attributes to the optimal transfer of thermal noise energy at the optimal cavity field detuning. We also investigate in detail the influence of the parametric gain, the pump phase, the oscillating frequency, the position of the atom and the temperature on the cooling and the thermophonon flux. The results obtained here have potential applications in evaluating thermal noise energy transport and preparation of functional thermal devices.

Enhancement of squeezing with cascaded and coherent feedback-controlled degenerate optical parametric amplifiers

The squeezing level of light on atomic resonance produced by a degenerate optical parametric amplifier (DOPA) is now limited by blue or violet pump-light-induced loss, and it is difficult to improve the squeezing by simply reducing the loss of DOPA. In this study, two promising schemes, namely, the cascaded DOPA (C-DOPA) and the coherent feedback-controlled DOPA (CFC-DOPA), are theoretically discussed. For a ideal case, the CFC-DOPA can realize infinite squeezing output but requires almost infinite accuracy in phase locking. For a practical case with feasible physical parameters of realistic systems, the performance of squeezing enhancement for the C-DOPA and CFC-DOPA is compared. The C-DOPA shows advantages in the megahertz frequency range, while the CFC-DOPA shows advantages in the low-frequency range. At a general analysis frequency of 2 MHz, C-DOPA shows better robustness against the loss of the system. As a price, it requires a smaller instability tolerance for phase locking. With the C-DOPA, the squeezing on Rb atomic resonance can be pushed from − 5 d B to − 7 d B . Our analytical results can provide a valuable reference for designing experimental devices to efficiently produce high-quality squeezed light on atomic resonance, which has potential applications in quantum information processing and quantum metrology.