BB84 quantum key distribution
Detect intercept-resend eavesdropping because measuring in an unknown basis creates errors.
Back to learning pathQuantum information applicationsWhy this experiment matters
What you will do
See how incompatible bases reveal interception before a raw key is accepted.
- 01
Alice sends random bits in either + or × basis.
- 02
Bob measures each qubit in a random basis.
- 03
Over an authenticated public channel, they keep matching bases and test a sample.
Predict before you measure
Choose one answer to unlock the measurement.
INTERACTIVE
Interactive model
Move the control, then run a measurement. This is a teaching simulation—not hardware output.
Choose one answer to unlock the measurement.
Predict before you measureMake a prediction, then run the measurement to reveal the expected and sampled results.
Measurement results
What the result shows
With no interception the sifted bits agree. Full intercept-resend produces a 25% sifted-key QBER, so the raw key is rejected.
GUIDED VIDEO
Watch the experiment
Follow the experiment with English narration and English subtitles.
See how incompatible bases reveal interception before a raw key is accepted.
Full transcript5 · 1:00
- 01Overview
See how incompatible bases reveal interception before a raw key is accepted.
- 02Experiment steps 1
Alice sends random bits in either + or × basis.
- 03Experiment steps 2
Bob measures each qubit in a random basis.
- 04Experiment steps 3
Over an authenticated public channel, they keep matching bases and test a sample.
- 05What to observe
With no interception the sifted bits agree. Full intercept-resend produces a 25% sifted-key QBER, so the raw key is rejected.
06 · CHECK
Check what you learned
Make a prediction, then run the measurement to reveal the expected and sampled results.