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Long-Time Storage of a Qubit Encoded in Decoherence-Free Subspace Using a Dual-Type Quantum Memory
1Tsinghua University, Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Beijing 100084, People's Republic of China.
Physical Review Letters
|December 19, 2025
Summary
Researchers developed a multi-ion quantum memory using a cryogenic trap, achieving over two hours of coherence time for entangled states. This advancement overcomes limitations of previous single-qubit systems for quantum information storage.
Area of Science:
- Quantum Information Science
- Atomic, Molecular, and Optical Physics
- Quantum Computing and Networking
Background:
- Quantum memory is crucial for quantum computation, networks, and metrology.
- Previous dual-species quantum memory achieved ~1 hour coherence but was limited to single qubits due to ion position hopping.
- Room-temperature traps and different ion masses hindered scalability and stability.
Purpose of the Study:
- To demonstrate a scalable multi-ion quantum memory with extended coherence times.
- To overcome the limitations of single-qubit storage in dual-species quantum memory systems.
- To explore the potential of cryogenic traps and same-mass ions for improved quantum memory performance.
Main Methods:
- Implemented a dual-type ion trap scheme in a cryogenic environment.
- Utilized sympathetic cooling with a coolant ion for memory ions of the same mass.
- Encoded qubits in decoherence-free two-ion entangled states.
- Applied error correction for dominant leakage errors.
Main Results:
- Achieved a multi-ion quantum memory with a coherence time exceeding two hours.
- Demonstrated qubit storage in entangled states within a decoherence-free subspace.
- Overcame ion position hopping issues by using a cryogenic trap and same-mass ions.
- Eliminated the need for an ultrastable frequency reference for the stored qubit.
Conclusions:
- The cryogenic dual-type scheme offers a scalable and stable platform for multi-ion quantum memory.
- This work significantly advances the coherence time and storage capacity for quantum information.
- The developed quantum memory is a promising building block for future quantum technologies.
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