Context: Scientists have developed a novel protocol to find out whether a pair of electrons is in an entangled state so that they can be safely used as resources for facilitating quantum information processing tasks. 

The protocol: 

  • The protocol has been developed through theoretical and experimental analysis by the scientists from S. N. Bose National Centre for Basic Sciences (SNBNCBS), Kolkata, an autonomous institute of the Department of Science and Technology.
  • In the protocol, the theoretical idea is based on applying the fine-grained uncertainty relation to perform quantum steering. 
  • The experiment uses an all-optical set-up in which entangled pairs of photons are created by laser light on Beta barium borate (BBO) crystals. 
  • The team concluded that the entangled pairs of photons generated by the laser and BBO crystals can be reliably used to perform secure communication tasks.

About Quantum Entanglement:

  • It is the physical phenomenon that occurs when a pair or group of particles is generated, interacting, in a way such that the quantum state of each particle of the pair or group cannot be described independently of the state of the others. 

Measuring entanglement: 

  • However, entanglement is fragile and is easily lost during the transit of photons through the environment. 
    • Hence it is extremely important to know whether a pair of photons is entangled, in order to use them as resources. 
  • Verification of entanglement requires the use of measurement devices, but such devices may be hacked or compromised by eavesdroppers. 
    • Device-independent self-testing (DIST) is a method that can be used in order to overcome such a possibility.
    • This method enables the verification of entanglement in an unknown quantum state of two photons without having direct access to the state, or complete trust in the measurement devices. 

Significance: Entangled states are key resources to facilitate many quantum information processing tasks and quantum cryptographic protocols.