Researchers from the University of Konstanz have made significant strides in converting matter qubits to traveling photonic qubits, a key aspect of quantum technologies. They have determined the upper limit for the photonic pulse emission efficiency of arbitrary matter qubit states and proposed a shift from optimizing the drive to optimizing the temporal mode of the flying qubit. The team also proposed protocols for time-bin encoding and spin-photon entanglement. Their work, which involves the use of stimulated Raman emission, has potential applications in quantum computing, quantum internet, and networking protocols.
What is the Significance of Matter Qubit to Traveling Photonic Qubit Conversion?
Conversion of matter qubits to traveling photonic qubits is fundamental to various quantum technologies. These include distributed quantum computing and several quantum internet and networking protocols. The process involves the use of stimulated Raman emission, a theory that applies to a wide range of physical systems. These systems include quantum dots, solid-state defects, and trapped ions, among others. The theory also applies to various parameter regimes.
The researchers, Benedikt Tissot and Guido Burkard from the Department of Physics at the University of Konstanz, Germany, have found the upper bound for the photonic pulse emission efficiency of arbitrary matter qubit states for imperfect emitters. They have also shown a path forward to optimizing the fidelity. Based on these results, they propose a paradigm shift from optimizing the drive to directly optimizing the temporal mode of the flying qubit using a closed-form expression.
The researchers have also proposed protocols for producing time-bin encoding and spin-photon entanglement. They suggest that the mathematical idea of using input-output theory for pulses to absorb the dominant emission process into the coherent dynamics, followed by a non-Hermitian Schrödinger equation approach, has great potential for studying other physical systems.
How Does Quantum Emission Play a Role in Quantum Technologies?
Efficient, tunable, and coherent quantum emitters are at the heart of many quantum technologies. These include entanglement distribution and more general applications for quantum networks and communication. These technologies can potentially enable a quantum internet with quantum mechanically enhanced security and privacy. Single-photon emission represents a cornerstone for several photonic technologies.
There is a great interest in coherent quantum media conversion as it allows the connection between different quantum systems with diverse properties. This enables hybrid quantum systems that combine the advantages of each subsystem. Such hybrid quantum systems can combine matter systems with beneficial properties for storage or computation, such as trapped ions, semiconductor qubits implemented via quantum dots and defects in solids, and superconducting circuits with easily transmittable photons.
Cavity-enhanced stimulated Raman emission is an established technique for controlled and nearly deterministic pulse emission. On-demand emission promises a leap towards the independence of emission and absorption, which is of the utmost importance when exchanging states between diverse systems.
What is the Fundamental Fidelity Bound of Coherent State Transfer?
In their paper, the researchers theoretically determine the fundamental fidelity bound of coherent state transfer for arbitrary pulse shapes from a stationary matter three-level system via a cavity to a traveling qubit pulse. This facilitates a distinct approach to maximize the state transfer fidelity. They are particularly interested in the transfer of a superposition of qubit states via the excited state and cavity to the traveling photon qubit.
Previously derived photon retrieval bounds, depending only on the cavity decay rate and cooperativity of the emitter-cavity coupling, can significantly overestimate the bound calculated by the researchers. Their bound includes additional system features, most prominently different emitter decoherence processes and the flying qubit’s temporal shape and initial superposition states. These are fundamentally necessary to understand spin-photon entanglement.
The researchers’ bound depends on the photon’s shape, making it suited for finding optimized flying qubit shapes. This provides a paradigm shift from approaches that aim to find the optimal drive, such as the shortcut, to the adiabaticity approach, as well as theories eliminating the propagating pulse.
How Can Stimulated Raman Emission Be Used in Quantum Technological Applications?
Stimulated Raman emission has quantum technological applications beyond single-photon sources. For example, it can be used to create a photon entangled with the matter qubit or to transfer the matter qubit to a time-bin qubit if an additional long-lived matter state or nuclear spin is available.
For instance, the researchers focus on the silicon-vacancy center in diamond, an established Raman emitter, which features the silicon nuclear spin as a quantum memory. They propose to use a nuclear CnNOT followed by a Raman emission resulting in the entangled state. The basic idea is to store the wave function amplitude of the qubit state in an ancillary state during the emission from the qubit state to the first time bin. After the first emission, gates are applied between the qubit and the ancillary states.
What is the Conclusion of the Research?
The researchers have shown how stimulated Raman emission can be used to generate spin-photon entanglement. They have introduced the model describing the emitter and the quantum pulse and presented a closed-form solution of the dynamics. They have also introduced the temporal mode matching to link the emitter dynamics to the temporal mode.
Using the solution, they have bounded the state transfer fidelity and shown how to optimize the pulse shape to increase the fidelity. The researchers conclude that their work has great potential for studying other physical systems and for further development in the field of quantum technologies.
The article named: Efficient high-fidelity flying qubit shaping, was published in Physical review research on 2024-02-08, . The authors are Benedikt Tissot and Guido Burkard. Find more at https://doi.org/10.1103/physrevresearch.6.013150.
The article “Efficient high-fidelity flying qubit shaping” by Benedikt Tissot and Guido Burkard, published in Physical Review Research, discusses the development of a new method for shaping flying qubits. Flying qubits are quantum bits that move freely in space and are considered crucial for the development of quantum computing and quantum communication systems. The authors present an efficient and high-fidelity method for shaping these qubits, which could significantly improve the performance of quantum systems. The article was published on February 8, 2024. For more information, you can visit the link provided.