[11599] in cryptography@c2.net mail archive
Re: Quantum computers inch closer?
daemon@ATHENA.MIT.EDU (David Honig)
Mon Sep 2 14:22:15 2002
Date: Mon, 02 Sep 2002 11:15:18 -0700
To: bear@sonic.net, cryptography@wasabisystems.com
From: David Honig <dahonig@cox.net>
In-Reply-To: <6b44b3a52d6bbe079046c7c2a0d44566@aarg.net>
At 08:56 PM 8/30/02 -0700, AARG!Anonymous wrote:
>Bear writes:
>> In this case you'd need to set up the wires-and-gates model
>> in the QC for two ciphertext blocks, each attached to an
>> identical plaintext-recognizer function and attached to the
>> same key register. Then you set up the entangled state,
>> and collapse the eigenvector on the eigenstate where the
>> ciphertext for block A and block B is produced, and the
>> plaintext recognizer for both block A and block B return
>> "1", and then you'd read the plaintext and key out of the
>> appropriate locations (dots?) in the qchip.
>
>The problem is that you can't forcibly collapse the state vector into your
>wished-for eigenstate, the one where the plaintext recognizer returns a 1.
>Instead, it will collapse into a random state, associated with a random
>key, and it is overwhelmingly likely that this key is one for which the
>recognizer returns 0.
I thought the whole point of quantum-computer design is to build
systems where you *do* impose your arbitrary constraints on the system.
The whole difficult part of q-computer design is getting enough
qubits to sit still to q-search the space of solutions
(to Bear's Feistel-gates-machine), subject
to your specific constraints (eg., here's a chunk of ciphertext;
here's a function which discriminates noise from likely plaintext, or
a set of likely plaintexts).
The *whole problem* is calculating/enforcing your problem constraints
on the q-system. No different from a sim annealing or evolution run,
where all the domain-tricks are in the eval function.
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