Adjoint-Via-Conjugation Annotations for Quantum Circuit Optimization
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Solution Overview
Problem
Existing quantum programming languages lack support for specialized programming patterns like conditional-adjoint and adjoint-via-conjugation, leading to inefficient use of qubits and increased circuit depth, as compilers fail to optimize circuits effectively.
Innovation Solution
The introduction of adjoint-via-conjugation annotations allows compilers to replace controlled operations with conditional-adjoint operations, utilizing idle qubits and reducing qubit requirements and circuit depth by leveraging cheaper implementations of quantum operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If controlled operations are used in quantum circuits, then the operations can be implemented with standard quantum gates, but the circuit depth increases and more qubits are required
Solution Approach 1:
The patent changes the operational parameters by replacing controlled operations with adjoint-via-conjugation operations. This parameter change allows the same computational functionality to be achieved with different gate sequences that have smaller depth and fewer qubit requirements, directly resolving the contradiction between execution efficiency and circuit complexity
Solution Approach 2:
The patent uses adjoint operations as a copy or alternative representation of controlled operations. By computing the adjoint (conjugate transpose) of the controlled operation, the patent creates an equivalent computational effect that can be implemented more efficiently, achieving the same result with reduced resource requirements
2Reliability
If clean qubits are used in quantum circuits, then the quantum program can be implemented with sufficient computational resources, but the total number of qubits required increases
Solution Approach 1:
The patent enables idle qubits to serve dual purposes: they maintain their unknown state while simultaneously being used for computational operations. The adjoint-via-conjugation technique allows these qubits to participate in computations without requiring initialization to clean states, making the quantum system more self-sufficient and reducing the need for additional clean qubits
Solution Approach 2:
The patent makes idle qubits universal by allowing them to perform multiple functions: maintaining quantum state information and participating in computational operations simultaneously. This multi-functionality eliminates the need for separate clean qubits, reducing the total qubit count while maintaining program correctness
Data Source
AI summary
None of the existing quantum programming languages provide specialized support for programming patterns such as conditional-adjoint or adjoint-via-conjugation. As a result, compilers of these languages fail to exploit the optimization opportunities mentioned in this disclosure. Further, none of the available quantum programming languages provide support for automatic translation of circuits using clean qubits to circuits that use idle qubits. Thus, the resulting circuits oftentimes use more qubits than would be required. Embodiments of the disclosed technology, thus allow one to run said circuits on smaller quantum devices. Previous multiplication circuits make use of (expensive) controlled additions. Embodiments of the disclosed technology employ multipliers that work using conditional-adjoint additions, which are cheaper to implement on both near-term and large-scale quantum hardware. The savings lie between 1.5 and 2× in circuit depth for large number of qubits.