Free-Fermionic Topological Quantum Sensors

Area of Science:

• Condensed Matter Physics
• Quantum Information Science

Background:

• Second-order quantum phase transitions offer enhanced sensing near criticality.
• Key features like symmetry breaking and long-range entanglement are thought to drive this enhancement.
• The precise mechanism responsible for quantum enhanced sensing remains unclear.

Purpose of the Study:

• To identify the specific features of quantum phase transitions responsible for enhanced sensing.
• To investigate quantum enhanced sensing in topological systems lacking symmetry breaking and long-range entanglement.
• To explore the role of gap closing in enabling quantum enhanced sensing.

Main Methods:

• Analytical investigation of phase transitions in free-fermionic topological systems.
• Focus on topological edge states near the phase boundary.
• Illustrative examples using the 1D Su-Schrieffer-Heeger chain and 2D Chern insulator models.

Main Results:

• Quantum enhanced sensing is demonstrated using topological edge states in systems without symmetry breaking or long-range entanglement.
• The enhancement persists in experimentally accessible ground states.
• Gap closing is identified as the primary candidate for the source of quantum enhanced sensing.
• A simple measurement strategy provides near-optimal precision for sensing using generic edge states.

Conclusions:

• Symmetry breaking and long-range entanglement are not essential for quantum enhanced sensing.
• Topological edge states offer a robust platform for quantum sensing.
• Gap closing is the crucial feature enabling quantum enhanced sensing, paving the way for topological quantum sensors.