Acceptor Qubits in Silicon for Fast Control and Decoherence Protection
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Solution Overview
Problem
Quantum computers face challenges in maintaining coherence and protecting quantum information from decoherence sources like charge noise and phonon coupling due to strong spin-orbit coupling, which affects the reliability of qubits in solid-state quantum computation.
Innovation Solution
The use of acceptor qubits in crystalline silicon, where acceptor atoms create a hole bound to form a qubit that can be manipulated between 'ON' and 'OFF' states using alternating and direct electric fields, with a pair of gates applying electric fields to control the qubit's spin and interaction strength, and reading out results as charge signals, effectively isolating time-reversal symmetric states to mitigate decoherence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If acceptor qubits are used in crystalline silicon, then rapid electrical manipulation of qubits is enabled, but susceptibility to decoherence from charge noise and phonon coupling increases
Solution Approach 1:
The patent implements dynamic switching between two operational states: an 'ON' state for rapid quantum manipulation and an 'OFF' state for protected storage. The system dynamically transitions between these states by controlling the coupling strength between the qubit and electric field, enabling fast operations when needed while maintaining coherence protection during storage periods
Solution Approach 2:
The patent changes the interaction parameter between the qubit and electric field by switching between weak coupling (protected state) and strong coupling (manipulation state). This parameter change allows the same qubit system to exhibit different coherence properties depending on the operational phase, resolving the contradiction between manipulation speed and coherence stability
2Ease of operation
If qubits are manipulated using electric fields, then rapid all-electrical control is achieved, but decoherence from charge noise and phonon coupling increases
Solution Approach 1:
The patent employs periodic alternating electric fields for qubit manipulation while maintaining the ability to switch to static or zero-field conditions for protection. The periodic nature of the control fields enables coherent manipulation when required, while the system can periodically transition to field-free states to minimize decoherence exposure during storage phases
3Loss of information
If quantum information is stored in manipulated basis, then computation results are retained, but decoherence affects the stored information over time
Solution Approach 1:
The patent performs preliminary switching to the protected 'OFF' state immediately after quantum manipulation is complete, before decoherence can significantly affect the stored information. This preliminary action of transitioning to the protected basis ensures that computation results are stored in a decoherence-resistant state, minimizing information loss over time
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for rapid electrical manipulation of qubits with reduced susceptibility to decoherence, enabling efficient storage and retrieval of quantum information by switching between 'ON' and 'OFF' states within the coherence time, thus enhancing the stability and reliability of quantum computations.
Implementation Method 1
manipulated by applying an alternating electric field; by which an alternating electric field is applied to the silicon to manipulate the qubit hole spin at resonance
Implementation Method 2
A source of external magnetic field may be applied to the acceptor atom to lift a four-fold degeneracy of a ground state of the acceptor atom to facilitate flips of the hole spin at resonance
Implementation Method 3
a direct electric field is applied to the silicon to manipulate the strength of the interaction between the qubit and the alternating electric field, that is the interaction strength between the qubit levels, to selectively switch the qubit between an 'ON' state
Data Source
AI summary
A quantum computer comprises of at least one qubit formed from holes created with acceptor atoms (10) in crystalline silicon (12) and a pair of gates (14, 16) located above the acceptor atoms (10) to apply direct electric field and alternating electric field for switching, manipulating the qubit such that quantum information resulting from being manipulated is stored from decoherence.