Why can information not be identified with physical systems? Again, what type of information are we talking about other than bits? Bits are not information. They just represent information and its actually not even information at all, it is just data.
The above questions touch on a few different topics, so I apologize if I don't address them systematically (also, the only sleep I've had in the past three days was a few hours and I've sort of spent all my time on looking into research practices, software, and participant recruitment/management/attrition/etc., so if I am incoherent, I apologize).
I think the first issue which requires some clarification is what I mean (and Susskind, the physicist in the video clip) mean by information. The link I included in my last post is a major contribution to information theory by Miller and therefore cognitive science, psychology, communications, etc. (as soon as you get off of the elevator at Harvard's William James Hall, there are a bunch of materials such as a first printing of Chomsky's
Syntactic Structures which were foundational in the cognitive and computer sciences; one of them is a plaque with a print of Miller's study).
The classical definition of information is in its simplist form one of possibilities. Language, binary code, morse code, genetic code, etc., all are capable of representing meaningful data because they can be "chunked" into units, and these units can have at least 2 states. In classical physics, entropy and information theory were for a while much almost as tied together as information theory is in modern (quantum) physics. But while computer science, linguistics, etc., increasingly used information/communications theory the use in physics decreased. The reason has to do with what information means when used formally.
As I said, information is more or less just possible states/alternatives. The ancient Greeks used pebbles to vote. But pebbles are only "information" when someone can interpret the states as meaningful in some way. The Greek use of pebbles did not make pebbles binary units (bits) of information. Their interpretation of the pebbles' states did.
Bits ARE information, as information is defined (formally) in terms of entropy or possible states of some physical entities, elements, etc. But they are not physical states or physical entities in and of themselves, anymore than any unit of measurement is. A computer bit has a particular physical realization, but it is far from the only possible physical instantiation of a binary unit, nor does any information unit require a direct correspondence with some physical entity or characteristic of some physical entity.
In classical mechanics, the use of words like "state" or "property" or "characteristic" had a clear meaning because they had a clear relation to a physical systen. A rock thrown from a particular hight at a certain speed with certain wind conditions could be described mathematically in terms of the location of the rock, the space the rock occupied, the velocity of the rock, and so forth. Every measurement or value of the system (a rock being thrown in some environment) corresponded quite clearly to some physical aspect of that system.
This is not true in quantum physics. There is no such relation. When we describe the "state" of a quantum system, this state has no physical reality. It's a vector space with particular properties (a Hilbert space). In order to describe actual physical properties, an entirely different formalism/method is required. Simplistically, a quantum system in some experiment exists in the physical world but it is described by the researchers using mathematical formalisms that do not directly relate to the system itself, nor is it clear what they mean. It is not clear, for example, whether a quantum system which is described as being in multiple states is actually in multiple states (a violation of classical logic and causality), or that this discription is simply a probability/statistical function.
When a quantum system is measured, the description of the system fails. Imagine throwing a rock in a lab designed with all kinds of devices to measure location, velocity, etc., but every time you throw the rock, the only way you can predict where the rock will end up is by describing it as existing in different places. However, you never actually observe the rock in multiple places. There are then two different steps when it comes to dealing with quantum systems. The first is the description, a mathematical transcription of the system which is based on theory, not on observations of the system itself (it can't be). Then you run the system (e.g., firing electrons at some detector). The description of the system you have represents the electrons as being in different states at the same time. But you never observe this, and you require another mathematical device (usually Hermetian operators) to describe the measurements.
In other words, while your "system" is completely described by your mathematical transcription, you will never actually be able to relate that description to anything physical. Doing so would be like actually observing the rock you throw as being in different places at the same time.
Qubits are used to describe the states of quantum systems. However, once again these "states" cannot be observed and it is not clear what they represent (i.e., how they correspond to the physical world). Unlike operators used in the measurement process, however, using an information theory approach makes the physical nature secondary and the problem of relating "states" of the system to to actual characteristics of it a non-issue. However, the mathematics used in QM describe reality isn't all that important in this sense, because the focus is only on possible states of a prepared system
after it is measured. Which makes the ontological status of the states and/or the physical system largely irrelevant. The important thing is only the initial set-up and the final states, which is the one thing in QM we know very well.
However, because the system is described in terms of multiple states, and we do not know how these states actually correspond to physical reality (does classical logic fail at the most fundamental level of reality? do physical systems violate causality?), there is no way to relate qubits to the actual quantum systems. They can only relate to the outcomes.