The interaction between quantum emitters and graphene wrapped nanowire has been investigated using a Green's function technique. The eigenmodes for the graphene wrapped nanowire at various Fermi levels in graphene have been solved exactly. The Dicke subradiance and superradiance resulting from the graphene-mediated interaction have been observed. Based on these phenomena, we have proposed a scheme for a deterministic tunable two-qubit quantum phase gate. The "switching" effect for the quantum phase gate has been realized theoretically by changing an external voltage, which is very beneficial for the quantum-information processing.
The dielectric cylinder covered with graphene (DCCG) is found to be a promising platform for studying multi-qubit collective effects. The plasmons supported by DCCG have huge wave numbers and low loss. Under some conditions, the zeroth- and first-order modes even have the same wavelength. Qubits along DCCG can interact with each other strongly by coupling with the plasmons within tens to hundreds of plasmonic wavelengths. Additionally, the electro-optical tunability of graphene means that we can manipulate the plasmonic wavelength and subsequently the dynamic evolutions of the qubits mediated by the DCCG conveniently. These properties make the graphene be a potential choice for quantum information device.
Inspired by the remarkable ability of plasmons to boost radiative emission rates, we propose leveraging acoustic graphene plasmons (AGPs) to realize tunable, giant Purcell enhancements for single-photon, entangled-photon, and multipolar quantum emitters. These AGPs are localized inside a cavity defined by a graphene sheet and a metallic nanocube and filled with a dielectric of thickness of a few nanometers and consisting of stacked layers of 2D materials, containing impurities or defects that act as quantum light emitters. Through finite-difference time domain (FDTD) calculations, we show that this geometry can achieve giant Purcell enhancement factors over a large portion of the infrared (IR) spectrum, up to 6 orders of magnitude in the mid-IR and up to 4 orders of magnitude at telecommunications wavelengths, reaching quantum efficiencies of 95\% and 89\%, respectively, with high-mobility graphene. We obtain Purcell enhancement factors for single-photon electric dipole (E1), electric quadrupole (E2), and electric octupole (E3) transitions and two-photon spontaneous emission (2PSE) transitions, of the orders of
104,
107,
109, and
109, respectively, and a quantum efficiency of 79\% for entangled-photon emission with high-mobility graphene at a wavelength of
λ=1.55 μm. Importantly, AGP mode frequencies depend on the graphene Fermi energy, which can be tuned via electrostatic gating to modulate fluorescence enhancement in real time. As an example, we consider the Purcell enhancement of spontaneous single- and two-photon emissions from an erbium atom inside single-layer (SL) WS
2. Our results could be useful for electrically tunable quantum emitter devices with applications in quantum communication and quantum information processing.
The Dicke subradiance and superradiance resulting from the interaction between surface plasmons of a nanosphere and an ensemble of quantum emitters have been investigated using a Green’s function approach. Based on such an investigation, we propose a scheme for a deterministic multi-qubit quantum phase gate. As an example, two-qubit, three-qubit, and four-qubit quantum phase gates have been designed and analyzed in detail. Phenomena due to the losses in the metal are discussed. Potential applications of these phenomena to quantum-information processing are anticipated.
The Dicke subradiance and superradiance resulting from the interaction between surface plasmons of nanospheres and an ensemble of quantum emitters have been investigated by using a Green's function approach. Based on such an investigation, we propose a scheme for a deterministic multi-qubit quantum phase gate. The case of single sphere has been compared with nanosphere cluster which possesses hot spots. The potential application of present phenomena to the quantum-information processing is anticipated.
A scheme to construct analogical atoms using graphene nanostructures via quantum nonlinearity is proposed. Due to the strong field localization capability of graphene plasmons and the significant intrinsic nonlinearity of graphene, a strong nonlinear optical response can be realized even with single-photon excitation. In this process, the quantum vacuum localized plasmonic mode plays a crucial role in achieving the third-order multi-photon nonlinear effect. The eigenfrequency of the nanostructure can shift by an amount tens of times larger than the decay rate, causing the nanostructure cavity to exhibit atomic-like behaviors. Furthermore, multilevel atoms can be constructed through the interaction of composite graphene nanostructures. The parameters of these atoms can be manipulated by adjusting the nanostructure size, Fermi energy, and other parameters. This research holds significant potential for applications in highly integrated, controllable nanophotonics.