Quantum Control Sequence for NISQ Hardware
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Solution Overview
Problem
Current quantum computers with noisy, intermediate-scale quantum (NISQ) hardware are limited by the number of qubits and decoherence time, making it difficult to implement complex quantum algorithms without error correction or fault-tolerance, which are resource-intensive.
Innovation Solution
Re-design quantum algorithms at a level below the quantum circuit model by expressing them as a series of k-qudit interactions and decomposing each interaction into single-qudit and two-qudit unitary rotations that account for the physical constraints of the quantum computer, allowing for more efficient and precise execution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If quantum algorithms are implemented using standard quantum circuit model with discrete gates, then algorithm design is convenient and standardized, but the circuit depth becomes too large and execution time exceeds decoherence time
Solution Approach 1:
The patent replaces the discrete gate-based quantum circuit model with a continuous-time quantum evolution model. Instead of applying a sequence of discrete quantum gates, the system directly implements continuous unitary transformations generated by Hamiltonian evolution. This substitution eliminates the overhead of gate decomposition and compilation, significantly reducing circuit depth and execution time while maintaining algorithmic functionality.
Solution Approach 2:
The patent changes the fundamental parameterization of quantum operations from discrete gate sequences to continuous evolution parameters. By parameterizing quantum operations in terms of continuous-time Hamiltonian evolution with adjustable evolution times and interaction strengths, the system can optimize execution duration to match decoherence time constraints while preserving the essential quantum computational processes.
2Adaptability or versatility
If more quantum gates are applied to increase algorithm complexity, then algorithm capability improves, but decoherence effects accumulate and reduce fidelity
Solution Approach 1:
The patent implements continuous quantum evolution without interruption by discrete gate boundaries. The quantum system evolves continuously under a time-dependent Hamiltonian, maintaining unbroken quantum coherence throughout the computation. This continuous action eliminates the cumulative decoherence effects that arise from repeated gate applications and measurements, preserving quantum state fidelity even for complex algorithms.
3Reliability
If error correction and fault-tolerance are implemented to maintain reliability, then quantum computation accuracy improves, but resource requirements and system complexity increase dramatically
Solution Approach 1:
The patent employs disposable ancillary qubits that are prepared, used for a single continuous evolution step, and then discarded. These short-lived auxiliary quantum systems enable error mitigation and computational flexibility without requiring permanent fault-tolerant architectures. The ancillary qubits are reset and reused in subsequent evolution steps, providing error correction capabilities with minimal resource overhead compared to full fault-tolerance schemes.
Data Source
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AI summary
A method is provided for determining a control sequence for performing a multiqudit algorithm on a quantum computer, the multiqudit algorithm expressible as a series of one or more k-qudit interactions. The method comprises, for each of the k-qudit interactions, decomposing the k-qudit interaction into a sequence of single-qudit unitary rotations and/or two-qudit unitary rotations from the continuous family of controllable unitary rotations generated by underlying physical interactions in the hardware of the quantum computer subject to a specified minimum interaction time, said sequence being physically implementable on the quantum computer. The method further comprises combining the sequences to form a combined interaction sequence. The method further comprises determining, based on the combined interaction sequence, the control sequence for performing the multiqudit algorithm on the quantum computer. The method may comprise, after the combining step, repeating the combined interaction sequence at least once to form a repeated interaction sequence. Determining the control sequence may comprise determining the control sequence based on the repeated sequence. The method is particularly suitable for performing simulations of the effects of Hamiltonians. Computer-readable media and computing apparatuses are also described.