Quantum Eigenstate Locking Using Energy-Updated Phase Gates
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Solution Overview
Problem
Current methods for preparing target quantum states are inefficient and prone to noise, especially when the initial state has limited overlap with the target state, leading to low probability of locking into the desired state.
Innovation Solution
An adaptive phase shift method is employed, where a quantum system and ancilla qubit are iteratively adjusted using a phase gate updated by a current average energy estimate, increasing the probability of locking into a target eigenstate and reducing noise-induced transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If current methods for preparing target quantum states are used, then the process can be implemented, but the efficiency is low and noise-induced transitions occur frequently
Solution Approach 1:
The patent implements feedback by iteratively measuring the quantum state and adjusting the phase gate parameter γ based on the measured energy expectation value. This closed-loop control continuously steers the system toward the target eigenstate, improving both convergence rate and reliability by correcting deviations caused by noise
Solution Approach 2:
The patent makes the phase gate parameter γ dynamic rather than static, updating it at each iteration based on current measurements. This dynamic adjustment allows the system to adapt to changing conditions and noise realizations, enhancing both the speed and reliability of state preparation
2Adaptability or versatility
If the initial state has limited overlap with the target state, then the quantum system can be prepared, but the probability of locking into the desired state decreases
Solution Approach 1:
The feedback mechanism measures the energy expectation value and adjusts γ accordingly, which effectively increases the overlap with the target state over time. This adaptive process works regardless of the initial overlap, making the method versatile while maintaining high reliability even when starting from states with limited overlap
Solution Approach 2:
The patent changes the parameter γ dynamically to optimize the transformation from the initial state to the target state. By adjusting this parameter based on measured energy, the system adapts to different initial conditions and maintains high probability of successful state preparation
3Productivity
If iterative adjustment methods are used, then the convergence rate improves, but the quantum circuit depth increases
Solution Approach 1:
The patent segments the state preparation process into discrete iterative steps, where each step uses a relatively simple phase gate operation. This segmentation allows the complex transformation to be achieved through multiple simple operations rather than one deep circuit, balancing convergence rate with manageable circuit depth at each iteration
Data Source
AI summary
Methods, systems and apparatus for targeting many-body states on a quantum computer. In one aspect, a method includes an adaptive phase shift method that includes preparing the quantum system in an initial state, wherein the initial state has non-zero overlap with the target eigenstate; preparing an ancilla qubit in a zero computational basis state; and iteratively applying a quantum eigenstate locking circuit to the quantum system and ancilla qubit until the state of the quantum system approximates the target eigenstate, wherein the quantum eigenstate locking circuit comprises a phase gate that, at each n-th iteration, is updated using a current average energy estimate of the quantum system.