Abstract: |
We describe a method for dense encoding of information. Bennet and Wiesner (Phys. Rev. Lett. 69:2881-2884, 1992), using EPR-pairs, showed that n bits can be encoded by n/2 quantum-bits, from which the original bits can be retrieved. Here, in a completely different (non-quantum) setting, we give a method for more dense encoding: In our method n bits x1,x2, . . . ,xn are mapped by a linear transform B over the 6-element ring Z6 to numbers z1,z2, . . . ,zt from ring Z6 with t=no(1)(i.e., much fewer numbers) (Quantity o(1) here denotes a positive number which goes to 0 as n goes to infinity), then, by applying another linear transform C to these zi's, we will get back n elements of ring Z6, x′1,x′2, . . . ,x′n, where, e.g., x′1 may have the form x′1=x1+3x2+4x3. One can get back x1 simply by running through the values of xi on the set 0,1,2,3,4,5, and noticing that only x1 has period 6, (3x2 has period 2, 4x3 has period 3). Our results generalize for any non-prime-power composite number m instead of 6. We also apply this method for fast computation of matrix multiplication and for compacting and extending matrices with linear transforms. |