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Background Suppression in Quantum Sensing of Dark Matter via $W$ State Projection

Shion Chen, Hajime Fukuda, Yutaro Iiyama, Yuya Mino, Takeo Moroi, Mikio Nakahara, Tatsumi Nitta, Thanaporn Sichanugrist

TL;DR

This work addresses the challenge of detecting ultra-weak wave-like dark matter signals with quantum sensors in the presence of noise. It introduces a protocol that projects sensor qubits onto the collective $W$ state to suppress non-collective noise while DM signals coherently populate the same subspace, avoiding the need for entanglement during accumulation. Analytically and numerically, the authors show that background suppression scales with the number of sensors $L$, achieving a significant improvement over separate measurements up to an optimal regime of $L$ and with a finite bandwidth $\Delta\omega_{\rm BW}$. The approach is general to various qubit sensors and may be extended with error-correction-inspired techniques, offering a practical path to enhanced DM searches with current quantum technologies.

Abstract

We show that measuring dark matter signal by projecting quantum sensors in the collective excited state can highly suppress the non-collective noise background, hence improving the sensitivity significantly. We trace the evolution of the sensors' state in the presence of both dark matter effect and sensors' decoherence effects, optimizing the protocol execution time, and show that the suppression of background by a factor equal to the number of sensors is possible. This method does not require the entanglement of sensors during the signal accumulation time, hence circumventing the difficulty of maintaining the lifetime of the entangled state that is present in other enhancement proposals. This protocol is also general regarding the type of qubit sensors.

Background Suppression in Quantum Sensing of Dark Matter via $W$ State Projection

TL;DR

This work addresses the challenge of detecting ultra-weak wave-like dark matter signals with quantum sensors in the presence of noise. It introduces a protocol that projects sensor qubits onto the collective state to suppress non-collective noise while DM signals coherently populate the same subspace, avoiding the need for entanglement during accumulation. Analytically and numerically, the authors show that background suppression scales with the number of sensors , achieving a significant improvement over separate measurements up to an optimal regime of and with a finite bandwidth . The approach is general to various qubit sensors and may be extended with error-correction-inspired techniques, offering a practical path to enhanced DM searches with current quantum technologies.

Abstract

We show that measuring dark matter signal by projecting quantum sensors in the collective excited state can highly suppress the non-collective noise background, hence improving the sensitivity significantly. We trace the evolution of the sensors' state in the presence of both dark matter effect and sensors' decoherence effects, optimizing the protocol execution time, and show that the suppression of background by a factor equal to the number of sensors is possible. This method does not require the entanglement of sensors during the signal accumulation time, hence circumventing the difficulty of maintaining the lifetime of the entangled state that is present in other enhancement proposals. This protocol is also general regarding the type of qubit sensors.

Paper Structure

This paper contains 9 sections, 76 equations, 2 figures.

Table of Contents

  1. Introduction
  2. Dark matter and noise model
  3. Dark matter detection with separate measurements
  4. Dark matter detection by projecting qubit sensors to $W$ state
  5. Discussion and Conclusion
  6. Review of the time evolution for the open quantum system
  7. Solving the Lindblad equation with perturbation theory
  8. Uncertainty of the parameter estimation
  9. Quantum Cramér-Rao bound

Figures (2)

  • Figure 1: The ratio $\delta \epsilon^{ (W)}/\delta \epsilon^{\rm (sep)}$ of the uncertainties of measuring the DM signal between the case using $W$ state and the separate measurement. The solid, dashed, and dotted lines correspond to $\gamma_2/\gamma_1 \simeq 1,10$ and $100$, respectively.
  • Figure 2: The ratio $\delta \epsilon_{\rm sweep}^{ (W)}/\delta \epsilon_{\rm sweep}^{\rm (sep)}$ of the uncertainties of measuring the DM signal with unknown frequency between the case using $W$ state and the separate measurement with $\gamma_2/\gamma_1=1$. The dash-dotted lines are the ratio for the case of a signal with a known frequency provided as reference lines. The uncertainty of $W$ state case is supported by the wider bandwidth for $L \gtrsim \gamma_2/\Gamma_0$.