X-Message-Number: 18721 Date: Fri, 08 Mar 2002 12:02:19 +0100 From: Henri Kluytmans <> Subject: Re: Simulation using qubits I wrote : >> And how do you read them out ?????? >> You would still need to perform more quantum logic, and you would >> still need 2^608 qubits to transfer result into, and then collapse >> those qubits, to be able to read out the bit content. >> And how do you perform the simulation itself without more qubits? Yvan Bozzonetti replied : >Assume we have 3 qbits, mark them "x" when they are in >a superposition state, so at start we have: xxx <snip> >digit is not the same, so the final state is: 0x1, here, one digit >remains in a superposition state. You don't read that state because The problem is : You want to know the answer. Therefore you will have to read it out somewhere. By reading out the qubits they will collapse. As soon as you read out the middle bit, then it will collapse into either a 1 or a 0. Furthermore, if you have only one qubit in superposition state than that qubit can be either 1 or 0. If you have two qubits there are 4 combinations possible. But maybe only three are allowed. How do you get to know all the allowed combinations ???? You will still have to transfer the answer to more qubits, and then let those qubits collapse, to get the answer(s) (i.e. to get to know all allowed combinations). In principle you can store information in a superposition of entangled qubits, but to read out all the information you will need to transfer the result to more qubits first. ==== An example : We have 3 qubits again. But they are in an entangled state. None of the qubits has collapsed. (I.e. the state is XXX.) However let's assume the allowed states are only 101 and 010, but you don't know that. However I do know, because I have performed some quantum algorithms that resulted in the elimination of all other states. (Note that any of the 3 qubits can be either 1 or 0, but only 2 total states of the 8 possible ones are allowed.) Now I send these 3 qubits in entangled state to you. How do you get to know all the combinations that are still stored in these 3 qubits ? PS: And we didn't even discuss the problem performing the simulation itself yet, only about reading the result out of the qubits. Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=18721