# Can the color of an object be entangled?

Based on the answer to another question asking "What properties can be entangled? the answer to the question was "any property". But with all due respects to the answer, I must admit I am somewhat confused on the following details. Must the property perhaps be a quantum number or related to a quantum number in some way? Experiments seem to always want to measure either spin or polarization. But what exactly determines what can be chosen to be entangled? This is why I chose something that would on the surface be described as a qualia. ( i.e. An emergent property and not fundamental.) As for example another emergent property would be "heat". Is there a laundry list of equations perhaps that must be satisfied in order to declare that a property can be entangled? Thank you.

• Do you mean "colour" as in colour charge of quarks? Jan 28, 2017 at 23:39
• Please provide a link to the question you are referring to. Jan 28, 2017 at 23:42
• -1. No research effort. Jan 28, 2017 at 23:44

You are dealing with elementary particles in entanglement, which don't have that many fundamental properties to begin with. So if you are asking, to give a silly example I know, can you entangle two colored socks, no.

The people who perform the entanglement experiments need to go to extreme lengths to keep their entangled particles isolated. That is a major problem for them, and for the development of quantum computers also, that is shielding from outside influencs.

Here is a list of quantum numbers and the associated properties they label Quantum Numbers.

I don't see why the OP's question should be considered silly. And I also don't follow Countto10's claim that two colored socks can't be entangled. Surely any two objects can be entangled. (Note that the OP question is one of principle, not of practice.)

However, I feel the OP's question is even a bit more abstract. He does not seem to be asking whether two objects of different color can be entangled, but rather whether 'redness' can be entangled with 'blueness' (in the same sense that 'upness' can be entangled with 'downness'). More concretely, something like two balls at different locations being entangled with each other, in principle completely indistinguishable except for their color, which is either red or blue. The entanglement would be such that if one is red, the other must be blue and vice versa. In other words, it is the usual Bell pair with `spin' replaced by 'color'.

I see no issue with this set-up. One does have to make clear what one means by 'color'. 'Spin' can be defined in terms of its measurement: it determines how something moves in a magnetic field, say. Similarly 'color' can be defined as the (coherent) light it emits when white light hits the object. This is determined by the molecules that make up the object. In other words what one conceptually would refer to as an 'entanglement of colors' would come down to an 'entanglement of molecules', which already sounds more 'down-to-earth'-ish (at least for a theoretical physicist). In this precise language it is no longer really a 'qualia' though, so if the OP is unhappy with this interpretation of his question, he can maybe rephrase things.

• +1 for your points. I don't consider the OP's post silly, (and I would avoid answering the question, rather than insult someone who asked a straightforward question, no matter how basic). I simply meant that my example was going to be silly as it involved, well socks. I should have spelt out the reasons why anything like a pair of socks could not in practice be entangled, and as you say, distinguished between principle and practice. I thought that to emphasise the care with which entanglement experiments are carried out was enough to make the point.
– user140606
Jan 29, 2017 at 13:05
• @Rubin Verresen Yes , you picked up on what I was trying to ask. I must admit I asked it rather poorly and can see it caused some consternation. My fault. I accept your answer and thank you! As a side note. You isolated my question to an entanglement of molecules with some specific properties that give rise to "color". I am wondering if there is a quantum mechanical limit to how many "qualia" can be entangled at the same time but that is for another time.
– user86411
Jan 29, 2017 at 23:33