From Brian Macfarland
In his letter, Bruce Harris describes his 8-year-old niece’s solution to keeping track of two entangled photons on different trajectories: paint one red and the other blue (11 May, p 31).
Of course, Felicity meant that one photon should be given a left-hand and the other a right-hand spin before sending them off, so that their emissions would shift to either end of the spectrum and thus differentiate them.
I suspect that rather than confusing her uncle, a mere adult, with complex explanations involving Doppler shifts, Felicity termed it painting them. It seems that she is destined to become a great teacher of quantum physics.
Watford, Hertfordshire, UK
