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Approximate exchange-only entangling gates for the three-spin-1/2 decoherence-free subsystem.

James R van Meter1,2, Emanuel Knill2,3

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This study introduces a new decoupling strategy for creating approximate entangling gates in quantum computing. This method simplifies the construction of essential quantum logic gates like the controlled-not gate for decoherence-free qubits.

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Area of Science:

  • Quantum Information Science
  • Quantum Computing Hardware

Background:

  • Decoherence-free subsystems protect logical qubits from collective noise.
  • Electrically defined quantum dots are promising for implementing these qubits.
  • Exact exchange-only entangling gates are difficult to realize.

Purpose of the Study:

  • To develop straightforward approximate entangling gates using a decoupling strategy.
  • To enable implementation of entangling Hamiltonians with aligned physical spins.
  • To assess the control complexity of implementing the controlled-not (CNOT) gate.

Main Methods:

  • Utilizing a decoupling strategy to derive approximate entangling gates.
  • Implementing Hamiltonians as linear combinations of logical Pauli products.
  • Investigating gate implementation without assumptions on physical spin alignment for self-inverse gates.

Main Results:

  • The decoupling strategy yields straightforward approximate entangling gates.
  • Evolution under specific entangling Hamiltonians is achievable.
  • The controlled-not (CNOT) gate can be implemented efficiently without spin alignment constraints.
  • Control complexity for fault-tolerant fidelities is competitive with existing methods.

Conclusions:

  • The proposed decoupling strategy offers a practical approach to constructing entangling gates.
  • This method enhances the feasibility of using decoherence-free subsystems in quantum computing.
  • The competitive control complexity makes this approach suitable for fault-tolerant quantum computation.