Why in the news?

  • Scientists in the U.S. are setting up a new experimental design that could let scientists test ideas at the intersection of quantum theory and general relativity.

Quantum Mechanics

  • What is it?:
    • It is the branch of physics that explains how sub-atomic particles, like electrons and photons, can behave both as particles and waves.
    • It is also known as Wave-particle duality, a fundamental principle of quantum physics.
  • Key Principles:
    • Particles can behave both as waves and particles – Wave-Particle duality.
    • A particle can exist in multiple states until measured – Superposition.
    • Two particles are related such that estimating one would give the details about the other – Entanglement.
    • The position and momentum of a particle can not be determined simultaneously – Uncertainty principle.

General Relativity

  • What is it?:
    • It is the modern theory of gravity proposed by Albert Einstein as an extension to Newtonian Law of Gravity.
    • It describes gravity as the curvature of space-time fabric caused by mass and energy rather than the conventional force concept.
  • Key Principles:
    • Massive objects like the stars are bending the space-time fabric, causing planets to orbit them – Space-Time curvature.
    • Time moves slower in stronger gravitational fields like that of a black hole – Time dilation.
    • In a closed system, acceleration and gravitational forces are indistinguishable – Equivalence Principle.

Quantum-Gravity Interface

  • Researchers propose using a network of entangled atomic clocks -placed kilometres apart- to probe how quantum theory and general relativity interact in a tangible way.
    • Entangle optical atomic clocks via a quantum network and place them at different gravitational potentials.
  • Entangled clocks experience different proper times because of their distinct gravitational environments.
  • When recombined and interfered, their collective quantum behaviour encodes information about how time -and by extension, gravity- is affected by quantum superposition.
  • This enables experimental tests of quantum theory in curved spacetime, potentially challenging or affirming foundational principles like unitarity, linearity, and the Born rule in this regime.