Phase-sensitive Parametric Amplifier Research Articles

QPSK to BPSK modulation format conversion byphase-sensitive parametric amplification inmulti-slot waveguides.

The optical modulation conversion of a quadrature phase-shift keying (QPSK) signal to two binary phase-shift keying (BPSK) signals is theoretically realized in a phase-sensitive amplification (PSA) conversion system. We propose a multi-slot silicon-carbon nanotube/polydimethylsiloxane hybrid waveguide to achieve high nonlinearity of 108 W -1 m -1 for improving PSA performance. Constellation diagrams, error vector magnitude, and bit error rate (BER) are used to investigate and measure the performance of the output. The results show that the converted BPSK signal has more than a 10dB higher signal-to-noise ratio than the QPSK signal with a BER threshold of 10-3. Furthermore, the system has great potential for hierarchical modulation of advanced format signals and long-distance transmission.

Parametric Amplifiers Based on Quantum Dots

Josephson parametric amplifiers (JPAs) approaching quantum-limited noise performance have been instrumental in enabling high fidelity readout of superconducting qubits and, recently, semiconductor quantum dots (QDs). We propose that the quantum capacitance arising in electronic two-level systems (the dual of Josephson inductance) can provide an alternative dissipationless nonlinear element for parametric amplification. We experimentally demonstrate phase-sensitive parametric amplification using a QD-reservoir electron transition in a CMOS nanowire split-gate transistor embedded in a 1.8GHz superconducting lumped-element microwave cavity, achieving parametric gains of -3 to +3 dB, limited by Sisyphus dissipation. Using a semiclassical model, we find an optimized design within current technological capabilities could achieve gains and bandwidths comparable to JPAs, while providing complementary specifications with respect to integration in semiconductor platforms or operation at higher magnetic fields.

Low-Noise Integrated Phase-Sensitive Waveguide Parametric Amplifiers

Low-noise optical amplifiers play a vital role in optical communications and signal processing. Recently, there has been a pursuit for compact, waveguide-based, parametric amplifiers which employ the four-wave mixing process relying on the 3 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rd</sup> order nonlinearity, χ <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">(3)</sup> , of the material. Here, we present an analytic model for the gain and noise figure of phase-sensitive parametric amplifiers based on nonlinear optical waveguides, which includes the impact of the linear loss of the waveguide. We provide insights into the importance of this loss for the gain, but more importantly also for the amplifier noise figure. In particular, we study waveguides based on Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> and find that a gain of 28 dB with a 0.8 dB noise figure is feasible in a 3 m long waveguide having a loss of 1.5 dB/m. We finally investigate the impact of the Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> waveguide cross section on the dispersion and the nonlinear coefficient for the improvement of PSA performance.

One-Pump Phase Sensitive Fiber Optical Parametric Amplifier With Dual-Core Fiber

The gain performance of one pump phase sensitive fiber optical parametric amplifier (PS-FOPA) in the dual-core fiber is numerically investigated without pump depleting. The effects of the core coupling coefficient(C), the pump wavelength and the initial signal phase on the gain of PS-FOPA are analyzed in detail. It shows that, the signal gain is greatly affected by different core coupling coefficients, and a flatter gain is achieved with suitable C value. Also, when the pump wavelength is greater than the zero-dispersion wavelength (ZDW), both the peak gain and gain bandwidth decrease with the increase of C, but the trend is opposite in case of the pump wavelength less than the ZDW. Additionally, the flatter and broader gain spectra are obtained by adjusting the initial signal phase in core 2. This simulation provides a detail analysis for the dual-core PS-FOPA, which is significant for the all optical fiber amplifier systems.

Measuring continuous-variable quantum entanglement with parametric-amplifier-assisted homodyne detection

Traditional method for measuring continuous-variable quantum entanglement relies on balanced homodyne detections, which are sensitive to vacuum quantum noise coupled in through losses resulted from many factors such as detector's quantum efficiency and mode mismatching between detected field and local oscillator. In this paper, we propose and analyze a new measurement method, which is realized by assisting the balanced homodyne detections with a high gain phase sensitive parametric amplifier. The employment of the high gain parametric amplifier helps to tackle the vacuum quantum noise originated from detection losses. Moreover, because the high gain parametric amplifier can couple two fields of different types in a phase sensitive manner, the proposed scheme can be used to reveal quantum entanglement between two fields of different types by using only one balanced homodyne detection. Furthermore, detailed analysis shows that in the multi-mode case, the proposed scheme is also advantageous over the traditional method. Such a new measurement method should find wide applications in quantum information and quantum metrology involving measurement of continuous variables.

Cavity electromechanics with parametric mechanical driving

Microwave optomechanical circuits have been demonstrated to be powerful tools for both exploring fundamental physics of macroscopic mechanical oscillators, as well as being promising candidates for on-chip quantum-limited microwave devices. In most experiments so far, the mechanical oscillator is either used as a passive element and its displacement is detected using the superconducting cavity, or manipulated by intracavity fields. Here, we explore the possibility to directly and parametrically manipulate the mechanical nanobeam resonator of a cavity electromechanical system, which provides additional functionality to the toolbox of microwave optomechanics. In addition to using the cavity as an interferometer to detect parametrically modulated mechanical displacement and squeezed thermomechanical motion, we demonstrate that this approach can realize a phase-sensitive parametric amplifier for intracavity microwave photons. Future perspectives of optomechanical systems with a parametrically driven mechanical oscillator include exotic bath engineering with negative effective photon temperatures, or systems with enhanced optomechanical nonlinearities.

Squeezing-enhanced Raman spectroscopy

The sensitivity of classical Raman spectroscopy methods, such as coherent anti-stokes Raman spectroscopy (CARS) or stimulated Raman spectroscopy (SRS), is ultimately limited by shot-noise from the stimulating fields. We present the complete theoretical analysis of a squeezing-enhanced version of Raman spectroscopy that overcomes the shot-noise limit of sensitivity with enhancement of the Raman signal and inherent background suppression, while remaining fully compatible with standard Raman spectroscopy methods. By incorporating the Raman sample between two phase-sensitive parametric amplifiers that squeeze the light along orthogonal quadrature axes, the typical intensity measurement of the Raman response is converted into a quantum-limited, super-sensitive estimation of phase. The resonant Raman response in the sample induces a phase shift to signal-idler frequency-pairs within the fingerprint spectrum of the molecule, resulting in amplification of the resonant Raman signal by the squeezing factor of the parametric amplifiers, whereas the non-resonant background is annihilated by destructive interference. Seeding the interferometer with classical coherent light stimulates the Raman signal further without increasing the background, effectively forming squeezing-enhanced versions of CARS and SRS, where the quantum enhancement is achieved on top of the classical stimulation.

An All-Optical Buffer Based on Non-Degenerate Phase-Sensitive Parametric Amplification

The scheme of an optical buffer exploiting phase-sensitive amplification based non-degenerate four-wave mixing is presented and theoretically analyzed. The noise figure of the proposed buffer is analytically and numerically estimated as a function of the number of circulations inside the buffer cavity. Two principal configurations are studied depending on the position of the amplification unit inside the cavity. The analysis is supported by split-step Fourier simulations, which reveal different aspects of the buffer's operation. The performance is also estimated for modulated signals in terms of Q -factor and compared to buffers utilizing phase-insensitive amplification.

Hamiltonian approach for optimization of phase-sensitive double-pumped parametric amplifiers.

In this work we applied a Hamiltonian formalism to simplify the equations of non-degenerate nonlinear four-wave mixing to the one-degree-of-freedom Hamiltonian equations with a three-parameter Hamiltonian. Thereby, a problem of signal amplification in a phase-sensitive double-pumped parametric fiber amplifier with pump depletion was reduced to a geometrical study of the phase portraits of the one-degree-of-freedom Hamiltonian system. For a symmetric case of equal pump powers and equal signal and idler powers at the fiber input, it has been shown that the theoretical maximum gain occurs on the extremal trajectories. However, to reduce the nonlinear interaction of waves, we proposed to choose the separatrix as the optimal trajectory on the phase plane. Analytical expressions were found for the maximum amplification, as well as the length of optical fiber and the relative phase of interacting waves allowing this amplification. Using the proposed approach, we optimized of the phase-sensitive parametric amplifier. As a result, the optimal parameters of the phase-sensitive amplifier were found and the maximum possible signal amplification was realized in a broad range of signal wavelengths.

Quantum tomography enhanced through parametric amplification

Quantum tomography is the standard method of reconstructing the Wigner function of quantum states of light by means of balanced homodyne detection. The reconstruction quality strongly depends on the photodetectors quantum efficiency and other losses in the measurement setup. In this article we analyze in detail a protocol of enhanced quantum tomography, proposed by Leonhardt and Paul [] which allows one to reduce the degrading effect of detection losses. It is based on phase-sensitive parametric amplification, with the phase of the amplified quadrature being scanned synchronously with the local oscillator phase. Although with sufficiently strong amplification the protocol enables overcoming any detection inefficiency, it was so far not implemented in the experiment, probably due to the losses in the amplifier. Here we discuss a possible proof-of-principle experiment with a traveling-wave parametric amplifier. We show that with the state-of-the-art optical elements, the protocol enables high fidelity tomographic reconstruction of bright non-classical states of light. We consider two examples: bright squeezed vacuum and squeezed single-photon state, with the latter being a non-Gaussian state and both strongly affected by the losses.

Parametric excitation of a SiN membrane via piezoelectricity

We develop a stoichiometric silicon nitride (SiN) membrane-based electromechanical system, in which the spring constant of the mechanical resonator can be dynamically controlled via piezoelectric actuation. The degenerate parametric amplifier is studied in this configuration. We observe the splitting of mechanical mode in the response spectra of a phase-sensitive parametric amplifier. In addition, we demonstrate that the quality factor Q of the membrane oscillator can be significantly enhanced by more than two orders of magnitude due to the coherent amplification, reaching an effective Q factor of ∼3 × 108 at room temperature. The nonlinear effect on the parametric amplification is also investigated, as well as the thermomechanical noise squeezing. This system offers the possibility to integrate electrical, optical and mechanical degrees of freedom without compromising the exceptional material properties of SiN membranes, and can be a useful platform for studying cavity optoelectromechanics.

Generation of frequency degenerate twin beams in Rb85 vapor.

We demonstrate a new phase-matching geometry for four-wave mixing processes in hot Rb85 vapor, in which all four fields propagate in different directions but two of them are degenerate in frequency. When used as a parametric amplifier with an injected seed, two types of quantum mechanically correlated twin-beam states, either frequency degenerate or nondegenerate, can be generated. The quantum noise reduction in the intensity difference is almost 7dB for the nondegenerate type and nearly 5dB for the degenerate type. The spatial nondegeneracy of the four waves allows a variety of configurations of parametric processes, leading to flexible control for both phase insensitive and sensitive parametric amplification. The spatially nondegenerate but frequency degenerate four-wave mixing process will find wide applications in quantum metrology, quantum communication, and quantum information of continuous variables.

Rapid High-Fidelity Single-Shot Dispersive Readout of Superconducting Qubits

The speed of quantum gates and measurements is a decisive factor for the overall fidelity of quantum protocols when performed on physical qubits with finite coherence time. Reducing the time required to distinguish qubit states with high fidelity is therefore a critical goal in quantum information science. The state-of-the-art readout of superconducting qubits is based on the dispersive interaction with a readout resonator. Here, we bring this technique to its current limit and demonstrate how the careful design of system parameters leads to fast and high-fidelity measurements without affecting qubit coherence. We achieve this result by increasing the dispersive interaction strength, by choosing an optimal linewidth of the readout resonator, by employing a Purcell filter, and by utilizing phase-sensitive parametric amplification. In our experiment, we measure 98.25% readout fidelity in only 48 ns, when minimizing read-out time, and 99.2% in 88 ns, when maximizing the fidelity, limited predominantly by the qubit lifetime of 7.6 us. The presented scheme is also expected to be suitable for integration into a multiplexed readout architecture.

Quantum mechanical treatment of parametric amplification in an absorptive nonlinear medium

Generally, loss phenomena are known to affect the quantum properties of a light wave. This paper describes a quantum mechanical treatment of parametric amplification in an absorptive nonlinear medium. An expression of the quantum mechanical field operator in such a physical system is presented based on the Heisenberg equation, using which the quantum properties of traveling light suffering from medium absorption are quantitatively evaluated. Calculations using the obtained operator indicate that some degradation of noise performance is caused by the absorption. The influence of the absorption on the squeezing performance in phase-sensitive parametric amplification is also evaluated.

Experimental implementation of a nonlinear beamsplitter based on a phase-sensitive parametric amplifier

Beamsplitters have played an important role in quantum optics experiments. They are often used to split and combine two beams, especially in the construct of an interferometer. In this letter, we experimentally implement a nonlinear beamsplitter using a phase-sensitive parametric amplifier, which is based on four-wave mixing in hot rubidium vapor. Here we show that, despite the different frequencies of the two input beams, the output ports of the nonlinear beamsplitter exhibit interference phenomena. We make measurements of the interference fringe visibility and study how various parameters, such as the intensity gain of the amplifier, the intensity ratio of the two input beams, and the one and two photon detunings, affect the behavior of the nonlinear beamsplitter. It may find potential applications in quantum metrology and quantum information processing.

Phase sensitive parametric fiber amplifier for the 2 μm wavelength range.

A widely tunable phase sensitive parametric fiber amplifier employing a three fiber stages configuration and operating in the 2 μm wavelength region is demonstrated. Phase sensitive gain levels of 30 dB and a gain variation of 20 dB were measured for a pulsed pump by determining the conversion efficiency near 2 μm when a signal at 1.281 μm was applied. The amplifier operates in the wavelength range of 1952 nm to 2098 nm, with its bandwidth being around 0.1 nm. The bandwidth can be controlled by the fiber lengths and their dispersion properties.

An optical multi wavelength oscillator based on fiber phase sensitive amplification

We introduce a new concept for photonic components, an optical multi wavelength oscillator based on fiber phase sensitive parametric amplification. Two experimental setups were demonstrated, one for a continuous wave pump and the second for a pulsed pump. For each setup, several simultaneous oscillating lines were observed. The spectral spacing of the emitted lines and their power variance depend on the physical properties of the system as well as the pump wavelength. The pulsed pump setup also offers tunability over hundreds of nanometers with several simultaneous oscillating lines.

Frequency-resolved noise figure measurements of phase (in)sensitive fiber optical parametric amplifiers.

We measure the frequency-resolved noise figure of fiber optical parametric amplifiers both in phase-insensitive and phase-sensitive modes in the frequency range from 0.03 to 3 GHz. We also measure the variation in noise figure due to the degradation in pump optical signal to noise ratio and also as a function of the input signal powers. Noise figure degradation due to stimulated Brillouin scattering is observed.

Optical signal to noise ratio improvement through unbalanced noise beating in phase-sensitive parametric amplifiers.

We investigate the beating of signal and idler waves, which have imbalanced signal to noise ratios, in a phase-sensitive parametric amplifier. Imbalanced signal to noise ratios are achieved in two ways; first by imbalanced noise loading; second by varying idler to signal input power ratio. In the case of imbalanced noise loading the phase-sensitive amplifier improved the signal to noise ratio from 3 to 6 dB, and in the case of varying idler to signal input power ratio, the signal to noise ratio improved from 3 to in excess of 20 dB.

The Coupled Nonlinear Schrödinger Equations Describing Power and Phase for Modeling Phase-Sensitive Parametric Amplification in Silicon Waveguides

The coupled nonlinear Schrödinger (NLS) equations describing power and phase of the optical waves are used to model phase-sensitive (PS) parametric amplification in a width-modulated silicon-on-insulator (SOI) channel waveguide. Through solving the coupled NLS equations by the split-step Fourier and Runge-Kutta integration methods, the numerical results show that the coupled NLS equations can perfectly describe and character the PS amplification process in silicon waveguides.