How is it possible that quantum phenomenons (e.g. superposition) are possible when all quantum particles are being constantly observed?

I don't understand how quantum mechanics (and therefore also quantum computers) can work given that while we work with quantum states, particles that this quantum state consist of cannot be observed, which is the most fundamental requirement.

If I am not mistaken, by "observed" we mean interaction with any other particle (photon, gluon, electron or whatever else). So my very important questions:

1. 
   

   Aren't the particles this quantum state consists of interacting with each other? Why doesn't that cause the state to collapse?

   
   



2. 
   

   Aren't all particles in the universe interacting with Higgs field and gravitons etc? Why doesn't that cause every quantum state to collapse?

   
   

I feel there is something very fundamental in quantum mechanics that I am not aware of, hence I would be very pleased to have these questions answered.

Answer

Aren't the particles this quantum state consists of interacting with each other? Why doesn't that cause the state to collapse?

We have a mathematical model for the observations we can make of any system in the micro world. This model is quantum mechanics and its predictions have been verified experimentally over and over again.

Observables are quantities we can measure about the particles and fields in the micro world. A main postulate is that to every observable there corresponds a quantum mechanical operator. These operators enter the quantum mechanical equations whose solutions given the boundary conditions describe a system in the micro world.

It is true that a quantum system is continually interacting within itself as described by the quantum model, and there can be continual interactions with the boundaries but interaction is not a synonym for a measurement. The continuous interactions are off mass shell, virtual, and within the bounds of the quantum mechanical solutions of specific energy levels and allowed states and conservation of quantum numbers. They are not measurements.

Aren't all particles in the universe interacting with Higgs field and gravitons etc? Why doesn't that cause every quantum state to collapse?

Collapse is fancy terminology for measurement . Nobody is measuring the higg's field continuous virtual exchanges that give mass to the elementary particles, nor the gravitons either. In fact gravitons are hypothetical particle because we have never measured one, in the way we have measured photons. Also nobody is measuring the virtual photons that keep the electrons in their energy levels around the nucleus.

The basic misconception is identifying "interaction" with measurement. A measurement necessarily means an interaction. An interaction is much more than a measurement.