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Quantum Trojan Insertion: Controlled Activation for Covert Circuit Manipulation

Jayden John, Lakshman Golla, Qian Wang

TL;DR

The paper tackles the threat of untrusted quantum compilers by introducing a controllable quantum Trojan that activates only under predefined input conditions. It details a DAG-based two-phase insertion method that places Trojan gates in empty circuit slots without increasing depth, preserving functionality when deactivated. Experimental results on RevLib benchmarks show minimal depth overhead and substantial alterations to output distributions (TVD ≈ 0.9) in many cases, highlighting covert manipulation risks. The work emphasizes the need for new defense strategies tailored to dynamic, conditionally activated Trojans in quantum circuits and compiler pipelines.

Abstract

Quantum computing has demonstrated superior efficiency compared to classical computing. Quantum circuits are essential for implementing functions and achieving correct computational outcomes. Quantum circuit compilers, which translate high-level quantum operations into hardware-specific gates while optimizing performance, serve as the interface between the quantum software stack and physical quantum machines. However, untrusted compilers can introduce malicious hardware Trojans into quantum circuits, altering their functionality and leading to incorrect results. In the world of classical computing, effective hardware Trojans are a critical threat to integrated circuits. This process often involves stealthily inserting conditional logic gates that activate under specific input conditions. In this paper, we propose a novel advanced quantum Trojan that is controllable, allowing it to be activated or deactivated under different circumstances. These Trojans remain dormant until triggered by predefined input conditions, making detection challenging. Through a series of benchmark experiments, we demonstrate the feasibility of this method by evaluating the effectiveness of embedding controlled trojans in quantum circuits and measuring their impact on circuit performance and security.

Quantum Trojan Insertion: Controlled Activation for Covert Circuit Manipulation

TL;DR

The paper tackles the threat of untrusted quantum compilers by introducing a controllable quantum Trojan that activates only under predefined input conditions. It details a DAG-based two-phase insertion method that places Trojan gates in empty circuit slots without increasing depth, preserving functionality when deactivated. Experimental results on RevLib benchmarks show minimal depth overhead and substantial alterations to output distributions (TVD ≈ 0.9) in many cases, highlighting covert manipulation risks. The work emphasizes the need for new defense strategies tailored to dynamic, conditionally activated Trojans in quantum circuits and compiler pipelines.

Abstract

Quantum computing has demonstrated superior efficiency compared to classical computing. Quantum circuits are essential for implementing functions and achieving correct computational outcomes. Quantum circuit compilers, which translate high-level quantum operations into hardware-specific gates while optimizing performance, serve as the interface between the quantum software stack and physical quantum machines. However, untrusted compilers can introduce malicious hardware Trojans into quantum circuits, altering their functionality and leading to incorrect results. In the world of classical computing, effective hardware Trojans are a critical threat to integrated circuits. This process often involves stealthily inserting conditional logic gates that activate under specific input conditions. In this paper, we propose a novel advanced quantum Trojan that is controllable, allowing it to be activated or deactivated under different circumstances. These Trojans remain dormant until triggered by predefined input conditions, making detection challenging. Through a series of benchmark experiments, we demonstrate the feasibility of this method by evaluating the effectiveness of embedding controlled trojans in quantum circuits and measuring their impact on circuit performance and security.

Paper Structure

This paper contains 16 sections, 1 equation, 5 figures, 1 table, 1 algorithm.

Table of Contents

  1. Introduction
  2. Background & Related Work
  3. Hardware Trojans
  4. Quantum Circuits
  5. Quantum Circuit Compilation and Trojans
  6. Related Works
  7. Threat Models
  8. Quantum Trojan and Analysis
  9. Trojan Insertion Process
  10. Improvements to Prior Approach
  11. Experiments Evaluation
  12. Experimental Setup
  13. Metrics for Evaluation
  14. Result Analysis
  15. Cost and Overhead Analysis
  16. ...and 1 more sections

Figures (5)

  • Figure 1: An example of a quantum circuit
  • Figure 2: Illustration of the untrusted compiler threat model. During the compile process, the malicious Trojans are inserted.
  • Figure 3: Example of Trojan insertion. When the switch is off (left), the circuit operates normally, maintaining its intended functionality. However, when the switch is on (right), the Trojan gates become active, altering the circuit's behavior.
  • Figure 4: The dashed pink boxes labeled '$\emptyset$' indicate empty slots (no operation) on the respective qubit in that column.
  • Figure 5: Distribution of Total Variation Distance (TVD) of benchmark circuits: TVD of obfuscated circuit and restored circuit are calculated and shown respectively. Selected circuits are simulated using Qiskit and the FakeValencia backend, incorporating noise into the simulation