X-Message-Number: 8613 Date: Fri, 19 Sep 1997 21:29:27 -0700 (PDT) From: John K Clark <> Subject: QM -----BEGIN PGP SIGNED MESSAGE----- In #8608 Andre Robatino <> On Thu, 18 Sep 97 Wrote: >the (slight) arbitrariness in the way one represents |psi> is not >unique to QM: in classical mechanics, the coordinates one uses to >describe a system are known only up to an arbitrary translation, >rotation, and uniform velocity. I can't really argue with that because "slight" is a subjective measure, personally I would rate it somewhat greater than slight and somewhat less than enormous. Let me give an example. A photon passes through a polarizing filter set in the vertical position, the photon can be described by the state vector |psi v>. Linearly polarized light can be synthesized by equal mixtures of left and right circularly polarized light, so our photon must also have a state vector associated with its left polarized state, we'll call it |psi L> and |<psi v/psi L>|^2 =1/2. The photon then encounters a second polarizer set at angel Q to the vertical. This changes the photon, it's new vertical and left state vectors are |psi' v> and |psi' L>. We always assume in all further calculations that <psi v/psi L><psi L/psi' v> = 1/2 *e^iQ but there is no physical reason why that must be true only that it could be, it's a purely arbitrary convention, a Martian might assume that <psi v/psi L><psi L/psi' v> =(1/squareroot 2) *e^-iQ and his physics would work just as well and give the same answers as ours. John K Clark -----BEGIN PGP SIGNATURE----- Version: 2.6.i iQCzAgUBNCNNFX03wfSpid95AQGj5gTtF4uh4saH10p/cXUEaC/vzJB57Hv7XEOG QSIPDFqVUKhCD5YONTwGjvpx4a8QRAMmBKb7RHxZgib1K6FAXmpLsNt90O9Z5CW9 lw+1ao0huETDtujtISK7gJcVYK8yDESng/0oXJEpYAzSe9ggIczD7pXq1ooNKDxG CNXhdzC0uYzrAx5SY90NM92YAzVuxBWVDDu9Bi7qHwYP4SuLncQ=q+fQ -----END PGP SIGNATURE----- Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=8613