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Journal ArticleDOI

High cooperativity in coupled microwave resonator ferrimagnetic insulator hybrids.

20 Sep 2013-Physical Review Letters (American Physical Society)-Vol. 111, Iss: 12, pp 127003-127003
TL;DR: The observation of strong coupling between the exchange-coupled spins in a gallium-doped yttrium iron garnet and a superconducting coplanar microwave resonator made from Nb demonstrates that exchange-Coupled systems are suitable for cavity quantum electrodynamics experiments, while allowing high integration densities due to their spin densities of the order of one Bohr magneton per atom.
Abstract: We report the observation of strong coupling between the exchange-coupled spins in a gallium-doped yttrium iron garnet and a superconducting coplanar microwave resonator made from Nb. The measured coupling rate of 450 MHz is proportional to the square root of the number of exchange-coupled spins and well exceeds the loss rate of 50 MHz of the spin system. This demonstrates that exchange-coupled systems are suitable for cavity quantum electrodynamics experiments, while allowing high integration densities due to their spin densities of the order of one Bohr magneton per atom. Our results furthermore show, that experiments with multiple exchange-coupled spin systems interacting via a single resonator are within reach.
Citations
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Journal ArticleDOI
TL;DR: Hybrid quantum circuits combine two or more physical systems, with the goal of harnessing the advantages and strengths of the different systems in order to better explore new phenomena and potentially bring about novel quantum technologies as discussed by the authors.
Abstract: Hybrid quantum circuits combine two or more physical systems, with the goal of harnessing the advantages and strengths of the different systems in order to better explore new phenomena and potentially bring about novel quantum technologies. This article presents a brief overview of the progress achieved so far in the field of hybrid circuits involving atoms, spins, and solid-state devices (including superconducting and nanomechanical systems). How these circuits combine elements from atomic physics, quantum optics, condensed matter physics, and nanoscience is discussed, and different possible approaches for integrating various systems into a single circuit are presented. In particular, hybrid quantum circuits can be fabricated on a chip, facilitating their future scalability, which is crucial for building future quantum technologies, including quantum detectors, simulators, and computers.

1,439 citations


Cites background from "High cooperativity in coupled micro..."

  • ...Recently, Huebl et al. (2012) reported a spin-cavity hybrid system with a higher cooperativity (∼ 1350)....

    [...]

Journal ArticleDOI
TL;DR: Some of the driving theoretical ideas and first experimental realizations of hybrid quantum systems and the opportunities and challenges they present are reviewed and offers a glance at the near- and long-term perspectives of this fascinating and rapidly expanding field.
Abstract: An extensively pursued current direction of research in physics aims at the development of practical technologies that exploit the effects of quantum mechanics. As part of this ongoing effort, devices for quantum information processing, secure communication, and high-precision sensing are being implemented with diverse systems, ranging from photons, atoms, and spins to mesoscopic superconducting and nanomechanical structures. Their physical properties make some of these systems better suited than others for specific tasks; thus, photons are well suited for transmitting quantum information, weakly interacting spins can serve as long-lived quantum memories, and superconducting elements can rapidly process information encoded in their quantum states. A central goal of the envisaged quantum technologies is to develop devices that can simultaneously perform several of these tasks, namely, reliably store, process, and transmit quantum information. Hybrid quantum systems composed of different physical components with complementary functionalities may provide precisely such multitasking capabilities. This article reviews some of the driving theoretical ideas and first experimental realizations of hybrid quantum systems and the opportunities and challenges they present and offers a glance at the near- and long-term perspectives of this fascinating and rapidly expanding field.

743 citations

Journal ArticleDOI
24 Jul 2015-Science
TL;DR: In this paper, the authors demonstrate the coherent coupling between a single-magnon excitation in a millimeter-sized ferromagnetic sphere and a superconducting qubit.
Abstract: Rigidity of an ordered phase in condensed matter results in collective excitation modes spatially extending to macroscopic dimensions. A magnon is a quantum of such collective excitation modes in ordered spin systems. Here, we demonstrate the coherent coupling between a single-magnon excitation in a millimeter-sized ferromagnetic sphere and a superconducting qubit, with the interaction mediated by the virtual photon excitation in a microwave cavity. We obtain the coupling strength far exceeding the damping rates, thus bringing the hybrid system into the strong coupling regime. Furthermore, we use a parametric drive to realize a tunable magnon-qubit coupling scheme. Our approach provides a versatile tool for quantum control and measurement of the magnon excitations and may lead to advances in quantum information processing.

555 citations

Journal ArticleDOI
TL;DR: In this paper, a new class of hybrid quantum systems based on collective spin excitations in ferromagnetic materials has led to a diverse set of experimental platforms which are outlined in this review article.
Abstract: Engineered quantum systems enabling novel capabilities for communication, computation, and sensing have blossomed in the last decade. Architectures benefiting from combining distinct and complementary physical quantum systems have emerged as promising platforms for developing quantum technologies. A new class of hybrid quantum systems based on collective spin excitations in ferromagnetic materials has led to the diverse set of experimental platforms which are outlined in this review article. The coherent interaction between microwave cavity modes and collective spin-wave modes is presented as the backbone of the development of more complex hybrid quantum systems. Indeed, quanta of excitation of the spin-wave modes, called magnons, can also interact coherently with optical photons, phonons, and superconducting qubits in the fields of cavity optomagnonics, cavity magnomechanics, and quantum magnonics, respectively. Notably, quantum magnonics provides a promising platform for performing quantum optics experiments in magnetically-ordered solid-state systems. Applications of hybrid quantum systems based on magnonics for quantum information processing and quantum sensing are also outlined briefly.

379 citations

Journal ArticleDOI
TL;DR: It is demonstrated that by dissipation engineering, a non-Markovian interaction dynamics between the magnon and the microwave cavity photon can be achieved, which enables a magnon gradient memory to store information in the Magnon dark modes, which decouple from the microwave cavities and thus preserve a long lifetime.
Abstract: Extensive efforts have been expended in developing hybrid quantum systems to overcome the short coherence time of superconducting circuits by introducing the naturally long-lived spin degree of freedom. Among all the possible materials, single-crystal yttrium iron garnet has shown up recently as a promising candidate for hybrid systems, and various highly coherent interactions, including strong and even ultrastrong coupling, have been demonstrated. One distinct advantage in these systems is that spins form well-defined magnon modes, which allows flexible and precise tuning. Here we demonstrate that by dissipation engineering, a non-Markovian interaction dynamics between the magnon and the microwave cavity photon can be achieved. Such a process enables us to build a magnon gradient memory to store information in the magnon dark modes, which decouple from the microwave cavity and thus preserve a long lifetime. Our findings provide a promising approach for developing long-lifetime, multimode quantum memories.

330 citations

References
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Journal ArticleDOI
R. H. Dicke1
TL;DR: In this article, the authors considered a radiating gas as a single quantum-mechanical system, and the energy levels corresponding to certain correlations between individual molecules were described, where spontaneous emission of radiation in a transition between two such levels leads to the emission of coherent radiation.
Abstract: By considering a radiating gas as a single quantum-mechanical system, energy levels corresponding to certain correlations between individual molecules are described. Spontaneous emission of radiation in a transition between two such levels leads to the emission of coherent radiation. The discussion is limited first to a gas of dimension small compared with a wavelength. Spontaneous radiation rates and natural line breadths are calculated. For a gas of large extent the effect of photon recoil momentum on coherence is calculated. The effect of a radiation pulse in exciting "super-radiant" states is discussed. The angular correlation between successive photons spontaneously emitted by a gas initially in thermal equilibrium is calculated.

5,672 citations

Journal ArticleDOI
09 Sep 2004-Nature
TL;DR: It is shown that the strong coupling regime can be attained in a solid-state system, and the concept of circuit quantum electrodynamics opens many new possibilities for studying the strong interaction of light and matter.
Abstract: The interaction of matter and light is one of the fundamental processes occurring in nature, and its most elementary form is realized when a single atom interacts with a single photon. Reaching this regime has been a major focus of research in atomic physics and quantum optics1 for several decades and has generated the field of cavity quantum electrodynamics2,3. Here we perform an experiment in which a superconducting two-level system, playing the role of an artificial atom, is coupled to an on-chip cavity consisting of a superconducting transmission line resonator. We show that the strong coupling regime can be attained in a solid-state system, and we experimentally observe the coherent interaction of a superconducting two-level system with a single microwave photon. The concept of circuit quantum electrodynamics opens many new possibilities for studying the strong interaction of light and matter. This system can also be exploited for quantum information processing and quantum communication and may lead to new approaches for single photon generation and detection.

3,452 citations

Journal ArticleDOI
TL;DR: In this paper, a pedagogical introduction to the physics of quantum noise and its connections to quantum measurement and quantum amplification is given, and the basics of weak continuous measurements are described.
Abstract: The topic of quantum noise has become extremely timely due to the rise of quantum information physics and the resulting interchange of ideas between the condensed matter and atomic, molecular, optical--quantum optics communities. This review gives a pedagogical introduction to the physics of quantum noise and its connections to quantum measurement and quantum amplification. After introducing quantum noise spectra and methods for their detection, the basics of weak continuous measurements are described. Particular attention is given to the treatment of the standard quantum limit on linear amplifiers and position detectors within a general linear-response framework. This approach is shown how it relates to the standard Haus-Caves quantum limit for a bosonic amplifier known in quantum optics and its application to the case of electrical circuits is illustrated, including mesoscopic detectors and resonant cavity detectors.

1,581 citations

Journal ArticleDOI
TL;DR: In this article, it was shown that the Jaynes-cummings model breaks down in the regime of ultrastrong coupling between light and matter, and that higher-order processes are possible.
Abstract: The Jaynes–Cummings model describes the interaction between a two-level system and a small number of photons. It is now shown that the model breaks down in the regime of ultrastrong coupling between light and matter. The spectroscopic response of a superconducting artificial atom in a waveguide resonator indicates higher-order processes.

1,180 citations

Journal ArticleDOI
09 Jul 2009-Nature
TL;DR: A two-qubit superconducting processor and the implementation of the Grover search and Deutsch–Jozsa quantum algorithms are demonstrated and the generation of highly entangled states with concurrence up to 94 per cent is allowed.
Abstract: By exploiting two key aspects of quantum mechanics — the superposition and entanglement of physical states — quantum computers may eventually outperform their classical equivalents. A team based at Yale has achieved an important step towards that goal — the demonstration of the first solid-state quantum processor, which was used to execute two quantum algorithms. Quantum processors based on a few quantum bits have been demonstrated before using nuclear magnetic resonance, cold ion traps and optical systems, all of which bear little resemblance to conventional computers. This new processor is based on superconducting quantum circuits fabricated using conventional nanofabrication technology. There is still a long way to go before quantum computers can challenge the classical type. The processor is very basic, containing just two quantum bits, and operates at a fraction of a degree above absolute zero. But the chip contains all the essential features of a miniature working quantum computer and may prove scalable to more quantum bits and more complex algorithms. Quantum computers, which harness the superposition and entanglement of physical states, hold great promise for the future. Here, the demonstration of a two-qubit superconducting processor and the implementation of quantum algorithms, represents an important step in quantum computing. Quantum computers, which harness the superposition and entanglement of physical states, could outperform their classical counterparts in solving problems with technological impact—such as factoring large numbers and searching databases1,2. A quantum processor executes algorithms by applying a programmable sequence of gates to an initialized register of qubits, which coherently evolves into a final state containing the result of the computation. Building a quantum processor is challenging because of the need to meet simultaneously requirements that are in conflict: state preparation, long coherence times, universal gate operations and qubit readout. Processors based on a few qubits have been demonstrated using nuclear magnetic resonance3,4,5, cold ion trap6,7 and optical8 systems, but a solid-state realization has remained an outstanding challenge. Here we demonstrate a two-qubit superconducting processor and the implementation of the Grover search and Deutsch–Jozsa quantum algorithms1,2. We use a two-qubit interaction, tunable in strength by two orders of magnitude on nanosecond timescales, which is mediated by a cavity bus in a circuit quantum electrodynamics architecture9,10. This interaction allows the generation of highly entangled states with concurrence up to 94 per cent. Although this processor constitutes an important step in quantum computing with integrated circuits, continuing efforts to increase qubit coherence times, gate performance and register size will be required to fulfil the promise of a scalable technology.

1,039 citations