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The fundamental noise limit of a phase-preserving amplifier at frequency $\omega /2\pi $ is the standard quantum limit $T_{q}=\hbar \omega /2k_{B}$. In the microwave range, the best candidates have been amplifiers based on superconducting…
A quantum-limited amplifier enables the amplification of weak signals while introducing minimal noise dictated by the principles of quantum mechanics. These amplifiers serve a broad spectrum of applications in quantum computing, including…
Recent progress in solid state quantum information processing has stimulated the search for ultra-low-noise amplifiers and frequency converters in the microwave frequency range, which could attain the ultimate limit imposed by quantum…
Amplifiers are crucial in every experiment carrying out a very sensitive measurement. However, they always degrade the information by adding noise. Quantum mechanics puts a limit on how small this degradation can be. Theoretically, the…
This short and opinionated review starts with a concept of quantum signals at microwave frequencies and focuses on the principle of linear parametric amplification. The amplification process arises from the dispersive nonlinearity of…
Sensitive measurement of electrical signals is at the heart of modern science and technology. According to quantum mechanics, any detector or amplifier is required to add a certain amount of noise to the signal, equaling at best the energy…
Linear parametric amplification is a key operation in information processing. Our interest here is quantum-limited parametric amplification, $i.e.$, amplification of quantum signals while adding the minimum amount of noise allowed by…
High-gain microwave amplifiers operating near quantum limit are crucial for development of quantum technology. However, a systematic theoretical modeling and simulations of their performance represent rather challenging tasks due to the…
We study the dynamics of a driven atomic Josephson junction that we propose as a parametric amplifier. By periodically modulating the position of the barrier, we induce a small current across the junction, serving as our input signal. The…
We have realized a microwave quantum-limited amplifier that is directional and can therefore function without the front circulator needed in many quantum measurements. The amplification takes place in only one direction between the input…
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…
We have constructed a new type of amplifier whose primary purpose is the readout of superconducting quantum bits. It is based on the transition of an RF-driven Josephson junction between two distinct oscillation states near a dynamical…
The advent of ultra-low noise microwave amplifiers revolutionized several research fields demanding quantum-limited technologies. Exploiting a theoretical bimodal description of a linear phase-preserving amplifier, in this contribution we…
It has recently become possible to encode the quantum state of superconducting qubits and the position of nanomechanical oscillators into the states of microwave fields. However, to make an ideal measurement of the state of a qubit, or to…
We characterize a novel Josephson parametric amplifier based on a flux-tunable quarter-wavelength resonator. The fundamental resonance frequency is ~1GHz, but we use higher modes of the resonator for our measurements. An on-chip tuning line…
Broadband quantum-limited amplifiers are essential for quantum information processing, yet challenges in design and fabrication continue to hinder their widespread applications. Here, we introduce the broadband merged-element Josephson…
Quantum-limited amplifiers, such as Josephson Traveling Wave Parametric Amplifiers (JTWPAs) and Josephson Parametric Amplifiers (JPAs), are essential components in quantum computers. They amplify low-power microwave signals from qubits at…
Amplifiers are ubiquitous in electronics and play a fundamental role in a wide range of scientific measurements. From a user's perspective, an ideal amplifier has very low noise, operates over a broad frequency range, and has a high dynamic…
With a large portfolio of elemental quantum components, superconducting quantum circuits have contributed to dramatic advances in microwave quantum optics. Of these elements, quantum-limited parametric amplifiers have proven to be essential…
Nature sets fundamental limits regarding how accurate the amplification of analog signals may be. For instance, a linear amplifier unavoidably adds some noise which amounts to half a photon at best. While for most applications much higher…