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Updated: Jul 20, 2026
06:42
Generation and Coherent Control of Pulsed Quantum Frequency Combs
Published on: June 8, 2018
Principles of control for decoherence-free subsystems
P Cappellaro1, J S Hodges, T F Havel
1Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
The Journal of Chemical Physics
|September 1, 2006
Summary
Protecting quantum information using decoherence-free subsystems (DFSs) is advanced by controlling noise. This study shows how dynamical decoupling and modulated pulses enable high-fidelity quantum gates on DFS-encoded qubits, even with unavoidable system excursions.
Area of Science:
- Quantum Information Science
- Quantum Computing
- Quantum Error Correction
Background:
- Decoherence-free subsystems (DFSs) offer a robust method for safeguarding quantum information against noise, particularly when noise possesses known symmetry properties.
- Theoretical frameworks exist for universal logic gates on DFS-encoded qubits within the subsystem, but practical implementations often face limitations due to natural Hamiltonians.
- Operating on encoded qubits without compromising DFS protection is crucial for realizing fault-tolerant quantum computation.
Purpose of the Study:
- To present principles for operating on encoded qubits within DFSs when natural Hamiltonians prevent confinement.
- To explore the use of dynamical decoupling to manage decoherence during necessary excursions outside the DFS.
- To demonstrate practical methods for high-fidelity quantum gate operations on DFS-encoded qubits in realistic scenarios.
Main Methods:
- Application of dynamical decoupling techniques to mitigate decoherence during qubit operations.
- Utilizing cumulant expansions to analyze the dependence of quantum gate fidelity on noise correlation time for a two-physical-qubit DFS.
- Employing numerical simulations of 'strongly modulating pulses' for Nuclear Magnetic Resonance (NMR) quantum information processing.
Main Results:
- Fidelity of quantum gates implemented via dynamical decoupling is shown to be dependent on the correlation time of the noise.
- Numerical simulations confirm that 'strongly modulating pulses' can achieve high-fidelity operations on multiple DFS-encoded qubits.
- Successful operations are contingent on the modulation rate being significantly faster than the noise correlation time.
Conclusions:
- Dynamical decoupling and strongly modulating pulses provide effective strategies for controlling decoherence and performing operations on DFS-encoded qubits.
- The presented principles are broadly applicable to various quantum information processor implementations utilizing DFS-encoded qubits.
- This work advances the practical realization of robust quantum computation by addressing limitations in Hamiltonian control.
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