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What is quantum key distribution?
An introduction to Quantum Key distribution (QKD). What are quantum keys and how can we use them?
Suggested age range: 16+
Questions and answers
If you've got any questions about this video, please email stemexpert@bt.com and we'll answer them here...
Qubits, how do they work and how will they help change computational calculations?
A classical computer stores bits as either 0 or 1.
A quantum computer stores qubits in a mixed state where they can (i) be BOTH 0 and 1 at the same time and (ii) can be linked or entangled with all the other qubits in the computer.

So imagine a classical computer with 100 bits. IF each bit can be 0 or 1 then the total number of different states that these 100 bits could represent is given by 2^100. A HUGE number (your calculator won't be able to handle it). But the classical computer can only address ONE of these at a time because each of the 100 bits has to be either 0 or 1.

Imagine a quantum computer with 100 qubits. Now – all qubits are BOTH 0 and 1, and so the 2^100 states can ALL be represented simultaneously!! This compute power is FAR beyond anything that a classical computer could ever achieve. And it is still only 100 qubits!!

Two provisos:
  1. There is only a very limited number of things you can do with an entangled ensemble of 100 qubits and this reduces the potential / means you have to be very cunning how you make use of this new power.
  2. No one has yet managed to make a 100 qubit machine – but they will one day.
Curriculum links
GCSE to A level transition   »   Networking   »   Network hardware
Data and information   »   Encryption   »   What is encryption?
Data structues and algorithms   »   data structures   »   Arrays
Computer networks   »   Networking hardware   »   Network hardware devices
Computer networks   »   Networking hardware   »   Network hardware devices
Computer networks   »   Security   »   Worms, trojans and viruses
Computer networks   »   Security   »   Defence against malware
Computer networks   »   Security   »   Encryption and authentication
Programming fundamentals   »   Software enginerring principles   »   Stages of software development
Software Project   »   Introduction
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