**Next message:**Spudboy100@aol.com: "Re: 137: Sheer blank-minded stupidity"**Previous message:**Amara Graps: "beta Pic dust"**In reply to:**Eliezer S. Yudkowsky: "The mathematics of effective perfection"**Next in thread:**Ben Goertzel: "RE: The mathematics of effective perfection"**Messages sorted by:**[ date ] [ thread ] [ subject ] [ author ]

Eliezer S. Yudkowsky wrote:

The second type of perpetual motion machine,

the quantum, notes that state-vector reduction

again reduces the volume of phase space.

A large volume of phase space, describing

the probability amplitude that an electron

is present at all points of space, collapses

into a single point which describes the electron

as being present at a single point in space.

State-vector reduction takes zillions of possible

superposed Universes and annihilates all but one of them.

Thus, it may be possible to build a quantum perpetual

motion machine in which the amplitudes "cold states"

tend to add up while the amplitudes of "hot states"

cancel out; effectively, this dumps waste heat into

a superposed state that gets blipped out of existence

when the quantum collapse occurs.

Since measurement on a quantum system seems to be

an irreversible process one would say that, performing

such a measurement, the entropy should increase

(John von Neumann,the projection postulate, about 1930).

But the entropy change occuring, without measurement,

in an isolated quantum system and the entropy change due

to measurement are, of course, different (in the later

case some amount of information can be obtained).

So, how this information gain must be paid for?

And, If we look for the entropy change when the unitary

evolution of a quantum system is interrupted by a

"sequence" of measurements, how does entropy change?

"Repeated" measurements, with same result, on a quantum

system, reiterate resettings of the evolving wave function.

It brings about even an impediment of the evolution, when

the temporal separation of the detections is reduced, and

the interaction approaches to "continuous" measurement.

Well, the answer seems to be that: "repeated" measurements

on a quantum system tends to decrease the entropy

of this quantum system; a "continuous" measurement

on a quantum system tends to reduce the entropy to zero.

Of course it is somewhat counter-intutive that "repeated"

measurements decrease the entropy of a quantum system.

This "Zeno" effect is, perhaps, suggesting another

perpetual motion weird machine!

scerir

**Next message:**Spudboy100@aol.com: "Re: 137: Sheer blank-minded stupidity"**Previous message:**Amara Graps: "beta Pic dust"**In reply to:**Eliezer S. Yudkowsky: "The mathematics of effective perfection"**Next in thread:**Ben Goertzel: "RE: The mathematics of effective perfection"**Messages sorted by:**[ date ] [ thread ] [ subject ] [ author ]

*
This archive was generated by hypermail 2b30
: Mon May 28 2001 - 09:50:31 MDT
*