Quantum computing uses qbits which have complex-
valued probability distributions. Computer
simulations of
quantum processes are widely known to exist. I
propose
building an "abacus" which mechanically simulates
qbits.
Specifically, one small part of the probability
amplitude of
a qbit
would be mechanically simulated using a car
tire
with a weight attached. The amplitude is represented
by
the momentum of the car tire, and the phase is
represented by the angular position. By adjusting the
weight and speed (filling the tire with some amount
of
sand and then spinning it up with an electric motor)
the
initial state of one small part of the qbit probability
amplitude is programmed. Many such tires would be
arranged on a shaft, resembling a giant spinning
treaded
kebab, to mechanically approximate a single qbit. To
add
qbits, two such spinning tire kebabs would be
brought into
contact such that they begin spinning at the same
speed.
To measure the state of the qbit, measure the mass
and
velocity of one tire at random.

This sounds more like an art installation than a meaningful simulation, but it might find a place in a Science Discovery Centre or the like, so we will award a bun - pending a critique by [xenzag].