A few basic questions about quantum information

[wywong]

Could someone provide me with simple answers to the following questions? I have tried to find the answers on the internet but most search results are beyond my comprehension.

1. What is the maximum number of qubits that a photon can carry?

2. If Alice packs a qubit in a photon and sends the photon to Bob who is running away at relativistic speed, is the qubit he retrieves unaffected by his speed?

3. When two particles (say an electron and a positron) merges to form another particle (say photon), it seems that quantum information is lost. Why is that not so?

4. When a quantum state is measured, decoherence occurs and the qubit is lost to the environment. How does the environment keep the qubit? For example, if a measuring apparatus makes N measurements, do the N qubits now reside in the apparatus? Can the qubits lost to the environment be theoretically read from the environment?

5. Some theories suggest that the energy fueling the big bang was provided by quantum fluctuation. Does that mean quantum fluctuation can create quantum information?

Many TIAs.

wywong

 

[Simon Bridge]

Could someone provide me with simple answers to the following questions?

It is unlikely that there will be an answer that is simple enough for you that won't also leave something important unsaid.

I have tried to find the answers on the internet but most search results are beyond my comprehension.

There is no royal road to knowledge ... you just have to learn the stuff.

...
Most of what you are asking concerns the abstract nature of the qubit - but "information" is all in our heads. Start thinking about what form the information takes: what physically happens to Bob when he "receives a qubit" from Alice.

This (PhD Thesis) discussion may help:
http://arxiv.org/pdf/quant-ph/0412063.pdf