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

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.