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arXiv:2105.10191 · Physical Review A

Deterministic preparation of W states via spin-photon interactions

Fatih Özaydin, Can Yesilyurt, Sinan Bugu, Masato Koashi

Published May 18, 2021• 29 citations
arXivHTMLPDF

Abstract

Spin systems such as silicon and nitrogen-vacancy centers in diamond, quantum dots, and quantum dot molecules coupled to optical cavities appear to be key elements for creating quantum networks by not only constituting the nodes of the network but also assisting the creation of photonic networks. Here we study the deterministic preparation of arbitrary-size $W$ states with spin systems. We present an efficient operation on three qubits, with two being the logical qubits and one being the ancillary qubit, where no interaction between the logical qubits is required. The proposed operation can create a $W$-type Einstein-Podolsky-Rosen (EPR) pair from two separable qubits and expand that EPR pair or an arbitrary-size $W$ state by one, creating a $W$-like state. Taking this operation as the fundamental building block, we show how to create a large-scale $W$ state out of separable qubits or double the size of a $W$ state. Based on this operation and focusing on nitrogen-vacancy centers in diamond as an exemplary spin system, we propose a setup for preparing $W$ states of circularly polarized photons, assisted by a single-spin qubit, where no photon-photon interactions are required. Next, we propose a setup for preparing $W$ states of spin qubits of spatially separated systems, assisted by a single photon. We also analyze the effects of possible imperfections in implementing the gates on the fidelity of the generated $W$ states. In our setups, neither postmeasurement nor postprocessing the states of spin or photonic qubit is required. Our setups can be implemented with current technology, and we anticipate that they will contribute to quantum science and technologies.

DOI
10.1103/physreva.103.052421

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Preparing large-scale multi-partite entangled states of quantum bits in each physical form such as photons, atoms or electrons for each specific application area is a fundamental issue in quantum science and technologies. Here, we propose a setup based on Pauli spin blockade (PSB) for the preparation of large-scale W states of electrons in a double quantum dot (DQD). Within the proposed scheme, two W states of n and m electrons respectively can be fused by allowing each W state to transfer a single electron to each quantum dot. The presence or absence of PSB then determines whether the two states have fused or not, leading to the creation of a W state of n + m - 2 electrons in the successful case. Contrary to previous works based on quantum dots or nitrogen-vacancy centers in diamond, our proposal does not require any photon assistance. Therefore the 'complex' integration and tuning of an optical cavity is not a necessary prerequisite. We also show how to improve the success rate in our setup. Because requirements are based on currently available technology and well-known sensing techniques, our scheme can directly contribute to the advances in quantum technologies and, in particular in solid state systems.
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We propose efficient schemes for universal quantum gates with the photon polarization states and electron spin states of nitrogen-vacancy (NV) centers in diamond embedded in optical microcavity. A hybrid polarization-spin controlled-NOT gate and a two-qubit controlled phase gate between NV centers in separated cavities are demonstrated in the weak-coupling regime without complex devices or interaction. The gates presented here are deterministic and can be applied directly to a variety of quantum information processing tasks. The feasibility analyses show that our schemes can be accomplished with high fidelity under current technologies and have wide potential applications in quantum communication and computation fields.
We demonstrate efficient schemes of deterministic entanglement generation and quantum state transfer (QST) with the nitrogen-vacancy (NV) centers in diamond confined in separated microtoroidal resonators via single-photon input-output process. Assisted by the polarization of input photon pulse and the electron spin state of NV center, high fidelity NV center entangled states and photonic entangled states can be generated, respectively. The analyses of experimental feasibility show that our schemes work well with low quality resonators and weak coupling between qubits, which may be beneficial for exploring large-scale quantum information processing with diamond-based solid-state devices.
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