A quantum protocol for sharing a secret amongst many parties

Sharing a secret … the quantum way.

Anyone who has sent an email will know that often information must be sent to several people: one sender and many receiving parties. Traditional quantum communication, such as quantum key distribution (QKD), does not allow this and is only of the peer-to-peer form.

Using structured light as quantum photon states, the Wits team showed how to distribute information from one sender to 10 parties. Scientists at the University of the Witwatersrand in Johannesburg, South Africa, have demonstrated a record-setting quantum protocol for sharing a secret amongst many parties.

By using quantum tricks, the secret can only be unlocked if the parties trust one another.

Professor Andrew Forbes from the School of Physics at Wits University said“In essence, each party has no useful information, but if they trust one another, then the secret can be revealed. The level of trust can be set from just a few of the parties to all of them. Importantly, at no stage is the secret ever revealed through communication between the parties: they don’t have to reveal any secrets. In this way, a secret can be shared in a fundamentally secure manner across many nodes of a network: quantum secret sharing.”

“Our work pushes the state-of-the-art and brings quantum communication closer to true network implementation. When you think of networks, you think of many connections, many parties, who wish to share information and not just two. Now we know how to do this the quantum way.”

Using structured photons, scientists were able to reach high dimensions. Structured light means ‘Patterns of light,’ and here, the team could use many patterns to push the dimension limit. More dimensions mean more information in the light and translate directly to larger secrets.

Journal Reference:
  1. Jonathan Pinnell et al., Experimental Demonstration of 11‐Dimensional 10‐Party Quantum Secret Sharing, Laser & Photonics Reviews (2020). DOI: 10.1002/lpor.202000012

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