Abstract Some heralded schemes are presented for realizing solid‐state quantum gates, including SWAP and gates. They are achieved by emitter‐photon scattering in 1D waveguides, and the qubits are encoded on the degenerate ground states of the solid‐state emitters. The schemes for these two quantum gates feature a filtering mechanism that the faulty scattering events between quantum emitters and photons can be mapped into the heralded photon losses. That is, the protocols can turn physical errors caused by system imperfections into the detection of photon polarization, which is advantageous for quantum information and quantum computation. Furthermore, no auxiliary solid‐state qubits are needed in our schemes, which reduces not only quantum resource but also error. The calculations reveal that the success probabilities and fidelities of the two quantum gates are high with current experimental technologies.
Implementations of Heralded Solid‐State SWAP and SWAPSWAP Gates through Waveguide‐Assisted Interactions
Abstract Some heralded schemes are presented for realizing solid‐state quantum gates, including SWAP and gates. They are achieved by emitter‐photon scattering in 1D waveguides, and the qubits are encoded on the degenerate ground states of the solid‐state emitters. The schemes for these two quantum gates feature a filtering mechanism that the faulty scattering events between quantum emitters and photons can be mapped into the heralded photon losses. That is, the protocols can turn physical errors caused by system imperfections into the detection of photon polarization, which is advantageous for quantum information and quantum computation. Furthermore, no auxiliary solid‐state qubits are needed in our schemes, which reduces not only quantum resource but also error. The calculations reveal that the success probabilities and fidelities of the two quantum gates are high with current experimental technologies.
Universal quantum gates play a critical role in quantum information processing. Here, based on the scattering property of photons off single emitters in one-dimensional waveguides, we present some heralded protocols for realizing controlled-not, Toffoli, and Fredkin gates on hybrid systems. The control qubit of our gates is encoded on a flying photon, and the target qubits are encoded in the degenerate ground states of the emitter. In our schemes, the faulty scattering processes between emitters and photons caused by system imperfections can be transformed into the detection of photon polarization. That is, our three quantum gates are accomplished in a heralded way. Moreover, the quantum circuits for the three gates are versatile and compact, and no additional qubits are required. With current technique on manipulating the emitter-waveguide system, our protocols may be experimentally feasible. This work provides an effective avenue for implementing quantum logic gates.
Abstract Photonic hyper-parallel quantum gates play a critical role in high-capacity quantum communication and fast quantum computing. Here, based on photon scattering in one-dimensional (1D) waveguides, we present some heralded schemes for constructing four-qubit hyper-controlled-not (hyper-CNOT) gates in two-photon systems. The qubits are encoded on both the polarization and spatial-mode degrees of freedoms (DOFs) of the photons, which can simplify the quantum circuit and reduce the quantum resource consumption. In our schemes, the faulty scattering events between photons and emitters caused by system imperfections can be filtered out and discarded. That is, our protocols for hyper-CNOT gates work in a heralded way. Our calculations show that, with great progress in the emitter-waveguide systems, our photonic hyper-CNOT gates may be experimentally feasible.
We propose two heralded schemes for generating multipartite Greenberger-Horne-Zeilinger (GHZ) and W states. They are realized by photon scattering in one-dimensional waveguides, and the qubits are encoded in the degenerate ground states of the quantum emitters. In our schemes, errors caused by the system imperfections and faulty photon scattering can be turned into detectable photon loss, which is advantageous for quantum information science. That is, our schemes for creating GHZ and W states work in a heralded way. Moreover, the generation of the two entangled states can be theoretically generalized to many-qubit cases in a straightforward way. Our calculations show that both the success probabilities and fidelities of our two schemes are high with current technique on manipulating quantum dots in slow-light photonic crystal waveguides.
Abstract Quantum logic gate forms the cornerstone of quantum computing. Here, two error‐detected, circuit‐compact, and fidelity‐robust SWAP and (SWAP) () gates are set for quantum‐dot (QD) spins with the aid of the scattering property of photon off QD fixed in double‐sided microcavity. For an ideal single‐photon scattering, the efficiencies and fidelities of both the SWAP and (SWAP) gates can, in principle, be close to unity. Otherwise, being directed against a nonideal scattering, the error‐detected units of two gates make their fidelities near perfect at the expense of slight reductions of their efficiencies. Moreover, the two quantum gates work in an error‐detected way and may be experimentally feasible with current technique on regulating the QD‐cavity system. Further, additional spin qubits are not required, thereby reducing both quantum resource usages and error rates.
Abstract Qudit‐based quantum gates offer several advantages over qubit‐based counterparts, such as higher information density, the ability to address more complex problems, and richer quantum operations. In this study, three realistic protocols are presented for implementing a 44‐dimensional (16D) two‐qudit controlled‐SUM (CSUM) gate, where the 4D control qudit and 4D target qudit are encoded in the polarization degree of freedom (DoF) and spatial DoF of two photons, respectively. The first protocol is implemented exclusively using linear optical elements without auxiliary resources, making it feasible with current optical technologies and achieving an efficiency of 1/9. The second protocol utilizes photon scattering by a microcavity‐quantum‐dot system, enabling the 16D CSUM gate to operate deterministically without postselection. The third protocol introduces an error‐heralded mechanism based on the second protocol, theoretically achieving unity fidelity. Moreover, all protocols operate without ancillary photons, offering the advantages of compact circuits and low cost while further promoting the development of high‐dimensional quantum computation.
Abstract Efficient ways are presented to accomplish photonic controlled‐phase‐flip gate and entangler with the assistance of imperfect double‐sided quantum‐dot‐microcavity systems, but without ancillary qubits. Compact quantum circuits for implementing entanglement swapping between photon pairs and electron pairs are then designed. Unity fidelities of the schemes can be achieved, and physical imperfections in the construction processes are detected by single‐photon detectors. Also, the efficiencies of the schemes can be further improved by repeating the operation processes when the undesired performances are detected. The evaluations show that the schemes are possible with current experiment parameters.