Single-sided Cavities Research Articles

Scalable Quantum Controlled Gates on Single-Photon Polarization Qubits Assisted by Nitrogen-Vacancy Centers Inside Single-Sided Optical Cavities

Scalable Quantum Controlled Gates on Single-Photon Polarization Qubits Assisted by Nitrogen-Vacancy Centers Inside Single-Sided Optical Cavities

Scheme for Bidirectional Quantum Teleportation of Unknown Electron-Spin States of Quantum Dots within Single-Sided Cavities

We represent the mutual swapping of two unknown states using bidirectional quantum teleportation (BQT) while transferring a single photon. In our BQT scheme, two users (Alice and Bob) can mutually teleport their two unknown states of the electron-spin in quantum dots (QDs) embedded in single-sided cavities. For this BQT scheme, we employ the interactions of a photonic spin (photon) and an electron-spin (excess electron) of QDs confined in a single-sided cavity, which is feasible in practice. The previous BQT scheme which used cross-Kerr nonlinearities (XKNLs) and X-homodyne detection was inevitable the decoherence effect in optical fibers. Consequently, the proposed BQT scheme can enhance an experimental implementation with the use of QD-cavity systems under the decoherence effect and this can also be realized with current technology, compared with the previous BQT scheme based on XKNLs.

Encoding scheme using quantum dots for single logical qubit information onto four-photon decoherence-free states

We designed an encoding scheme, using quantum dots (QDs), for single logical qubit information by encoding quantum information onto four-photon decoherence-free states to acquire immunity against collective decoherence. The designed scheme comprised of QDs, confined in single-sided cavities (QD-cavity systems), used for arbitrary quantum information, encoded onto four-photon decoherence-free states (logical qubits). For our scheme, which can generate the four-photon decoherence-free states, and can encode quantum information onto logical qubits, high efficiency and reliable performance of the interaction between the photons and QD-cavity systems is essential. Thus, through our analysis of the performance of QD-cavity systems under vacuum noise and sideband leakage, we demonstrate that the encoding scheme for single logical qubit information could be feasibly implemented.

Optical Fredkin gate assisted by quantum dot within optical cavity under vacuum noise and sideband leakage

We propose a deterministic Fredkin gate which can accomplish controlled-swap operation between three-qubit states. The proposed Fredkin gate consists of a photonic system (single photon) and quantum dots (QDs) confined in single-sided cavities (two electron spin states). In our scheme, the control qubit is the polarization state of the single photon, and two electron spin states in QDs play the role of target qubits (swapped states by control qubit). The interaction between a photon and an electron of QD within the cavity (QD-cavity system) significantly affects the performance of Fredkin gate. Thus, through the analysis of the QD-cavity system under vacuum noise and sideband leakage, we demonstrate that reliable interaction and performance of the QD-cavity system with photonic state (photon) can be acquired in our scheme. Consequently, the Fredkin gate proposed in this paper can be experimentally implemented with high feasibility and efficiency.

Photonic scheme of discrete quantum Fourier transform for quantum algorithms via quantum dots

We propose an optical scheme of discrete quantum Fourier transform (DQFT) via ancillary systems using quantum dots (QDs) confined in single-sided cavities (QD-cavity systems). In our DQFT scheme, the main component is a controlled-rotation k (CRk) gate, which utilizes the interactions between photons and QDs, consisting of two QD-cavity systems. Since the proposed CRk gate can be experimentally implemented with high efficiency and reliable performance, the scalability of multi-qubit DQFT scheme can also be realized through the simple composition of the proposed CRk gates via the QD-cavity systems. Subsequently, in order to demonstrate the performance of the CRk gate, we analyze the interaction between a photon and a QD-cavity system, and then indicate the condition to be efficient CRk gate with feasibility under vacuum noise and sideband leakage.

Scheme for encoding single logical qubit information into three-photon decoherence-free states assisted by quantum dots

We propose an optical scheme to encode quantum information into three-photon decoherence-free states (single logical qubit information) and thereby acquire immunity from collective decoherence. Our scheme consists of quantum dots (QDs) within single-sided optical cavities and linearly optical devices for generation of three-photon decoherence-free states (logical qubits) and for encoding arbitrary quantum information. In our proposition, the interaction between photons and electron spin in the QD-cavity system is the critical component and plays the role of a quantum controlled operation to perform the processing of single logical qubit information with immunity against collective decoherence. Thus, we also analyze the performance of interaction between a photon and an electron in a QD. Consequently, for generating three-photon decoherence-free state encoded arbitrary quantum information, our scheme using QD-cavity systems is feasible. In practice, it could be implemented experimentally with current technologies.

Entanglement Purification on Separate Atoms in an Error-Detected Pattern

We propose an entanglement purification protocol (EPP) for purifying separate atoms embedded in single-sided optical cavities. The protocol works in an error-detected pattern, the reflection coefficients only appear as a global coefficient, the success or failure cases are heralded by the detection of photons, these merits make the protocol more robust and practical. We discuss the performance of the protocol with current experimental parameters, the results show the success probability of the present EPP is relatively high. The EPP could provide a promising building block for quantum repeaters and quantum networks in the future.

Hybrid Quantum Gates: High‐Fidelity Hybrid Quantum Gates between a Flying Photon and Diamond Nitrogen‐Vacancy Centers Assisted by Low‐Q Single‐Sided Cavities (Ann. Phys. 1/2019)

In article number 1800312, Ming Li, Jia-Ying Lin, and Mei Zhang propose a high-fidelity hybrid quantum Toffoli gate between a flying photon and diamond nitrogen-vacancy centers assisted by low-Q single-sided cavities. Photon detectors are employed to herald errors that occur in the practical input-output processes, which brings along the high fidelity while trading off a little efficiency.

Robust universal photonic quantum gates operable with imperfect processes involved in diamond nitrogen-vacancy centers inside low-Q single-sided cavities.

Robust universal quantum gates with an extremely high fidelity hold an important position in large-scale quantum computing. Here, we propose a scheme for several robust universal photonic quantum gates on a two-or three-photon system, including the controlled-NOT gate, the Toffoli gate, and the Fredkin gate, assisted by low-Q single-sided cavities. In our scheme, the quantum gates are robust against imperfect process occurring with the photons and the electron spins in diamond nitrogen-vacancy (NV) centers inside low-Q cavities. Errors due to the imperfect process are transferred to some heralding responses, which may lead to a direct recycling procedure to remedy the success probability of the quantum gates. As a result, the adverse impact of the imperfect process on fidelity is eliminated, greatly relaxing the restrictions on implementation of various quantum gates in experiments. Furthermore, the scheme is designed in a compact and heralded style, which can increase the robustness against environmental noise and local fluctuation, thus decreasing the operation time, the error probability, and the quantum resource consumption in a large-scale integrated quantum circuit. The near-unity fidelity and not-too-low efficiency with current achievable experimental techniques guarantees the feasibility of the scheme.

Heralded entangling quantum gate via cavity-assisted photon scattering

We theoretically investigate the generation of heralded entanglement between two identical atoms via cavity-assisted photon scattering in two different configurations, namely either both atoms confined in the same cavity or trapped into locally separated ones. Our protocols are given by a very simple and elegant single-step process, whose key mechanism is a controlled-phase-flip gate implemented by impinging a single photon on single-sided cavities. In particular, when the atoms are localized in remote cavities, we introduce a single-step parallel quantum circuit instead of the serial process extensively adopted in the literature. We also show that such parallel circuit can be straightforwardly applied to entangle two macroscopic clouds of atoms. Both protocols proposed here predict a high entanglement degree with a success probability close to the unity for the state-of-the-art parameters. Among other applications, our proposal and its extension to multiple atom-cavity systems step toward a suitable route for quantum networking, in particular for quantum state transfer, quantum teleportation and nonlocal quantum memory.

Constructions of secure entanglement channels assisted by quantum dots inside single-sided optical cavities

We propose quantum information processing schemes to generate and swap entangled states based on the interactions between flying photons and quantum dots (QDs) confined within optical cavities for quantum communication. To produce and distribute entangled states (Bell and Greenberger-Horne-Zeilinger [GHZ] states) between the photonic qubits of flying photons of consumers (Alice and Bob) and electron-spin qubits of a provider (trust center, or TC), the TC employs the interactions of the QD-cavity system, which is composed of a charged QD (negatively charged exciton) inside a single-sided cavity. Subsequently, the TC constructs an entanglement channel (Bell state and 4-qubit GHZ state) to link one consumer with another through entanglement swapping, which can be realized to exploit a probe photon with interactions of the QD-cavity systems and single-qubit measurements without Bell state measurement, for quantum communication between consumers. Consequently, the TC, which has quantum nodes (QD-cavity systems), can accomplish constructing the entanglement channel (authenticated channel) between two separated consumers from the distributions of entangled states and entanglement swapping. Furthermore, our schemes using QD-cavity systems, which are feasible with a certain probability of success and high fidelity, can be experimentally implemented with technology currently in use.

Scheme for secure swapping two unknown states of a photonic qubit and an electron-spin qubit using simultaneous quantum transmission and teleportation via quantum dots inside single-sided optical cavities

We propose a scheme for swapping two unknown states of a photon and electron spin confined to a charged quantum dot (QD) between two users by transferring a single photon. This scheme simultaneously transfers and teleports an unknown state (electron spin) between two users. For this bidirectional quantum communication, we utilize the interactions between a photonic and an electron-spin qubits of a QD located inside a single-sided optical cavity. Thus, our proposal using QD-cavity systems can obtain a certain success probability with high fidelity. Furthermore, compared to a previous scheme using cross-Kerr nonlinearities and homodyne detections, our scheme (using QD-cavity systems) can improve the feasibility under the decoherence effect in practice.

Quantum noise and squeezing in an optical parametric oscillator with arbitrary output-mirror coupling. II. Extension to double-sided cavities.

We treat quantum fluctuations and squeezing of the field generated by a degenerate optical parametric oscillator operating below threshold. The analysis reported here extends our previous calculations for single-sided cavities to double-sided cavities with arbitrary transmission coefficients for the two bounding mirrors.