Multi-Controlled NOT Quantum Circuit With Reduced Gate Depth

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Solution Overview

Problem

Existing quantum circuits for multi-controlled NOT gates require large circuit depths, leading to prolonged computation times, especially when implementing these gates using basic gates and varying auxiliary qubit and gate arrangements.

Innovation Solution

A quantum circuit design that minimizes circuit depth by utilizing a first auxiliary circuit, a quantum gate group, and a second auxiliary circuit, employing Toffoli gates or alternative quantum logic gates like CH, CZ, and CS gates to perform controlled NOT operations on target and auxiliary qubits, allowing for parallel operations and reduced depth.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If basic gates and auxiliary qubits are used to implement multi-controlled NOT gate, then the gate can be implemented on hardware platform, but circuit depth increases leading to longer computation time

Engineering Contradiction:
ImproveImplementability on hardware platformVSAvoidComputation time
Core Design Contradiction:
Ease of manufactureVSLoss of time

Solution Approach 1:

The patent segments the multi-controlled NOT gate implementation into multiple layers (first auxiliary circuit, quantum gate group, second auxiliary circuit) that can be executed in parallel. This segmentation allows the circuit to be divided into independent operational stages, reducing the sequential depth and enabling parallel execution to decrease computation time while remaining compatible with hardware platforms.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent introduces auxiliary qubits as an additional dimension resource to reduce circuit depth. By adding these auxiliary quantum bits, the implementation can distribute control logic across multiple qubits simultaneously, enabling parallel operations that reduce the temporal dimension (computation time) while maintaining hardware compatibility.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

2Productivity

If circuit depth is reduced for faster computation, then computation speed improves, but implementation complexity may increase

Engineering Contradiction:
ImproveComputation speedVSAvoidCircuit structure complexity
Core Design Contradiction:
ProductivityVSDevice complexity

Solution Approach 1:

The patent uses auxiliary qubits as intermediary elements that facilitate the reduced-depth implementation. These intermediary qubits act as mediators between control qubits and the target qubit, enabling parallel controlled operations that reduce circuit depth and increase computation speed, while the structured use of these intermediaries keeps the overall complexity manageable through systematic gate grouping.

Inventive Principle:
Principle #24Intermediary (Mediator)

3Loss of time

If more auxiliary qubits are used to reduce circuit depth, then computation time decreases, but device resource consumption increases

Engineering Contradiction:
ImproveComputation timeVSAvoidNumber of auxiliary qubits
Core Design Contradiction:
Loss of timeVSQuantity of substance

Solution Approach 1:

The patent optimizes the number of auxiliary qubits by changing the structural parameters of the circuit implementation. Through careful parameter selection in the gate group configuration and layer structure, the patent achieves the minimum necessary auxiliary qubits to enable parallel operations that reduce computation time, balancing resource consumption with performance improvement.

Inventive Principle:
Principle #35Parameter changes

Data Source

PatentUS20250266841A1Quantum circuit for implementing a multi-controlled not gate
Publication Date: 2025.08.21 ELECTRONICS & TELECOMM RES INST
  • US20250266841A1 patent drawing
  • US20250266841A1 patent drawing
  • US20250266841A1 patent drawing

AI summary

Disclosed is a quantum circuit for implementing multi-controlled NOT gates with N control qubits. A quantum circuit for implementing multi-controlled NOT gates with N control qubits according to one embodiment of the present disclosure may include a first auxiliary circuit that corresponds to one or more initial layers of a plurality of layers and performs a controlled NOT operation on a target qubit based on an Nth control qubit from among the N control qubits and a first auxiliary qubit initialized to a |+> state, a quantum gate group that corresponds to the plurality of layers and performs controlled NOT operation on the first auxiliary qubit based on first to (N−1)th control qubits, and a second auxiliary circuit that corresponds one or more last layers of the plurality of layers and performs controlled NOT operation on the target qubit based on the Nth control qubit and the first auxiliary qubit.