Quantum computing with trapped ions (0809.4368v1)

Abstract: Quantum computers hold the promise to solve certain computational task much more efficiently than classical computers. We review the recent experimental advancements towards a quantum computer with trapped ions. In particular, various implementations of qubits, quantum gates and some key experiments are discussed. Furthermore, we review some implementations of quantum algorithms such as a deterministic teleportation of quantum information and an error correction scheme.

• The paper presents a comprehensive review of experimental breakthroughs in implementing trapped ion qubits and high-fidelity quantum gates.
• The study details successful creation of entangled states and advancements in sympathetic cooling that enhance coherence and reduce decoherence.
• The paper outlines scalable quantum computing implications, including deterministic teleportation and robust error correction strategies.

Quantum Computing with Trapped Ions

The paper "Quantum computing with trapped ions" presents a comprehensive review of experimental advancements towards building quantum computers using trapped ions. This field of research promises significant computational breakthroughs, addressing tasks that exceed the capabilities of classical computers, particularly for quantum mechanical problems. The review highlights key experiments in implementing qubits and quantum gates, and discusses the progress in quantum algorithms, including deterministic teleportation and error correction schemes.

Overview of Ion Trap Quantum Computing

Ion trap quantum computing leverages the principles of quantum mechanics, specifically employing ions as qubits, the basic unit of quantum information. The quantum information is stored in the internal quantum states of ions, which are manipulated and measured using laser light. Trapped ion systems are considered highly advanced among other physical implementations due to their scalable nature and ability to perform high-fidelity gate operations.

Key Experimental Advances

1. Qubit Implementation and Initialization: The fundamental unit of quantum information, the qubit, is implemented using stable internal states of trapped ions, such as electronic or hyperfine states. Early ion-trap experiments established methods for initializing ions in precise quantum states, which is crucial for reliable quantum computation.
2. Quantum Gates and Algorithms: The experimental realization of various quantum gates has been a significant focus. The Cirac-Zoller and Mølmer-Sørensen gates are amongst the notable two-qubit gates realized. These gates enable the entanglement necessary for quantum operations. The deterministic teleportation of quantum states and quantum error correction are successes that exemplify the implementation of more complex quantum algorithms using these gates.
3. Entangled States: The formation of entangled states with trapped ions has been a foundational achievement. Entangled states are critical for quantum computing and quantum communication, demonstrated through the violation of Bell inequalities and generation of multi-ion entangled states like GHZ and W states.
4. Sympathetic Cooling and Ion Transport: Efficient quantum operations require ions to be cooled near their motional ground state. Experiments in sympathetic cooling, where additional ions are used to cool the ion of interest without disturbing its quantum state, have shown potential for reducing decoherence during quantum computation. Transporting ions through segmented traps while preserving quantum coherence is another key development that supports scalable quantum computing.

Implications and Future Directions

The findings and advancements documented in this review underline the promising trajectory of ion trap experiments. Practical implications span from quantum simulations to solutions in complex optimization and factorization problems. The theoretical exploration dovetails with experimental implementations, enhancing the fidelity and scalability of quantum computers.

Continued efforts aim to improve gate fidelities beyond error correction thresholds, potentially incorporating hybrid systems with other quantum technologies, such as superconducting qubits, to harness complementary strengths. The pursuit of more sophisticated traps with reduced heating rates and enhanced coherence times is ongoing, pointing towards a robust, universal quantum computing framework.

Conclusion

Overall, the progress in ion trap quantum computing showcases a strategically promising approach toward practical quantum computation. The continual enhancements in coherence, gate implementation, and scalability mechanisms highlight the maturation of trapped ion systems as viable quantum computational platforms. Further integration with other technology advancements may accelerate the realization of a scalable and efficient quantum computer.