We introduce a q-weighted version of the Robinson-Schensted (column
insertion) algorithm which is closely connected to q-Whittaker functions (or
Macdonald polynomials with t=0) and reduces to the usual Robinson-Schensted
algorithm when q=0. The q-insertion algorithm is `randomised', or `quantum', in
the sense that when inserting a positive integer into a tableau, the output is
a distribution of weights on a particular set of tableaux which includes the
output which would have been obtained via the usual column insertion algorithm.
There is also a notion of recording tableau in this setting. We show that the
distribution of weights of the pair of tableaux obtained when one applies the
q-insertion algorithm to a random word or permutation takes a particularly
simple form and is closely related to q-Whittaker functions. In the case 0≤q<1, the q-insertion algorithm applied to a random word also provides a new
framework for solving the q-TASEP interacting particle system introduced (in
the language of q-bosons) by Sasamoto and Wadati (1998) and yields formulas
which are equivalent to some of those recently obtained by Borodin and Corwin
(2011) via a stochastic evolution on discrete Gelfand-Tsetlin patterns (or
semistandard tableaux) which is coupled to the q-TASEP process. We show that
the sequence of P-tableaux obtained when one applies the q-insertion algorithm
to a random word defines another, quite different, evolution on semistandard
tableaux which is also coupled to the q-TASEP process
