Quantum interference device for controlled two-qubit operations

Loft, N. J. S.; Kjærgaard, Morten; Kristensen, Lasse Bjørn; Andersen, Christian Kraglund; Larsen, T. W.; Gustavsson, Simon; Oliver, William; Zinner, N. T.

doi:10.1038/s41534-020-0275-3

Cited by 15 publications

(14 citation statements)

References 57 publications

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“…As previously mentioned, the plasmon is a quasiparticle boson state exhibiting both particle and wave-like properties; hence, these quantum properties can be investigated to expand the scope of quantum mechanics-related devices and sensing applications. [12,33,[57][58][59] For example, coherency, entanglement, and tunneling can be further explored in quantum interferencebased devices, [60,61] single-photon emitters and detectors, [62,63] and quantum networks. [64][65][66][67] The quantum effect is explained further (in terms of the sub-nanometer size gap between two resonators) in the last section of this review.…”

Section: Classical and Quantum Nanoplasmonics: From Bulk Nano And Cluster Scales Down To Atomic Mattermentioning

confidence: 99%

Quantum Plasmonics: Energy Transport Through Plasmonic Gap

2021

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scanning tunneling microscopy (STM), [5,6] atomic force microscopy (AFM), [7] and other techniques allowing resolution to be reduced to the atomic scale can help realize atomic-scale world exploration. This is the starting point of the nanotechnology era; since its inception, this technology has changed the nature of almost every human-made object. Six decades after Richard Feynman's lecture, we find that there is still plenty of room at the bottom, through the incorporation of nanophotonics. [8] To elucidate: quantum plasmonics has emerged as an attractive research field in new nanophotonics; research is underway to reveal and accurately describe the quantum nature of electrons at the bottom of extremely confined nano-or sub-nanometer scale materials, using light. [9,10] By exploring the quantum mechanical interactions of matter with light (in particular, using the coherent interactions between the plasmonic cavity and the material), [11][12][13][14][15][16][17][18] these efforts seek to establish new frontiers in information processing technology and to satisfy the everincreasing requirements for speed and capacity in quantum computing, quantum cryptography, and quantum metrology. They might also suggest research fields beyond this, involving the ultimate miniaturization of photonic components and the extreme limits of the light-matter interaction. These advantages may help solve some fundamental problems of electronics, such as those of bandwidth, frequency, and energy consumption. [19] In this review, we describe recent developments in the research of exotic materials capable of mediating quantum plasmonics and inducing quantum energy transport. We briefly provide classical and quantum descriptions of matter, from the bulk, nano, and cluster scales down to atomic matter, exploring the band structures via their optical responses. By considering a single nanoplasmonic material, we describe the theoretical and experimental findings pertaining to assembled nanoplasmonic structures, in the context of the plasmonic gap distance and the type of advanced functional material. The plasmonic gap herein refers to a nanometer or sub-nanometer gap that transports (couples, tunnels, exchanges, confines) electromagnetic energy between plasmonic resonators. Advanced functional materials within an extremely confined metallic resonator are described; these include air/vacuum, aliphatic and conjugated molecules, 2D materials, organic and inorganic materials with At the interfaces of metal and dielectric materials, strong light-matter interactions excite surface plasmons; this allows electromagnetic field confinement and enhancement on the sub-wavelength scale. Such phenomena have attracted considerable interest in the field of exotic material-based nanophotonic research, with potential applications including nonlinear spectroscopies, information processing, single-molecule sensing, organic-molecule devices, and plasmon chemistry. These innovative plasmonics-based technologies can meet the ever-increasing demands for speed and ca...

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Section: Classical and Quantum Nanoplasmonics: From Bulk Nano And Cluster Scales Down To Atomic Mattermentioning

confidence: 99%

Quantum Plasmonics: Energy Transport Through Plasmonic Gap

2021

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“…An example of an entangling four‐qubit gate is the diamond gate, [ 40 ] which is an entangling swapping gate with two controls, which must be in an entangled state in order to control the swapping operation. The diamond gate is difficult to synthesize into one‐ and two‐qubit gates.…”

Section: Resultsmentioning

confidence: 99%

“…Once the saturation point is achieved, the only remaining parameter to change is the type of multi‐qubit gate in each layer. We find that highly entangling multi‐qubit gates, such as the cnot gate or the diamond gate [ 40 ] reach the saturation point of the relative expressibility,

scriptE

and entangling capability,

scriptC

, with less single‐qubit rotations compared to less entangling gates.…”

Section: Discussionmentioning

confidence: 99%

Reducing the Amount of Single‐Qubit Rotations in VQE and Related Algorithms

et al. 2020

Self Cite

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With the advent of hybrid quantum classical algorithms using parameterized quantum circuits, the question of how to optimize these algorithms and circuits emerges. In this paper, it is shown that the number of single-qubit rotations in parameterized quantum circuits can be decreased without compromising the relative expressibility or entangling capability of the circuit. It is also shown that the performance of a variational quantum eigensolver (VQE) is unaffected by a similar decrease in single-qubit rotations. Relative expressibility and entangling capability are compared across different number of qubits in parameterized quantum circuits. High-dimensional qudits as a platform for hybrid quantum classical algorithms is a rarity in the literature. Therefore, quantum frequency comb photonics is considered as a platform for such algorithms and it is shown that a relative expressibility and entangling capability comparable to the best regular parameterized quantum circuits can be obtained.

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“…5(d). This can, e.g., be useful if one want to study qutrit systems [95][96][97], or the leakage from the qubit states to higher states [98,99]. In this case the operators will be represented as 3 × 3 matrices, the matrix representation of the step operators become…”

Section: Three-level Modelmentioning

confidence: 99%

The superconducting circuit companion -- an introduction with worked examples

Rasmussen,

Christensen,

Pedersen

et al. 2021

Preprint

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This article is a tutorial on the quantum treatment of superconducting electrical circuits. It is intended for new researchers with limited or no experience with the field, but should be accessible to anyone with a bachelor's degree in physics or similar. The tutorial has three parts. The first part introduces the basic methods used in quantum circuit analysis, starting from a circuit diagram and ending with a quantized Hamiltonian truncated to the lowest levels. The second part introduces more advanced methods supplementing the methods presented in the first part. The third part is a collection of worked examples of superconducting circuits. Besides the examples in the third part, the two first parts also includes examples in parallel with the introduction of the methods.

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Quantum interference device for controlled two-qubit operations

Cited by 15 publications

References 57 publications

Quantum Plasmonics: Energy Transport Through Plasmonic Gap

Quantum Plasmonics: Energy Transport Through Plasmonic Gap

Reducing the Amount of Single‐Qubit Rotations in VQE and Related Algorithms

The superconducting circuit companion -- an introduction with worked examples

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