Almost but not quite. With light the electric field can go negative and the average is generally 0. With sound in air the pressure component has a ”DC” offset of 1bar and it cannot go negative, you will just get nonlinear effects when you start nearing that limit.
The DC offset can be considered as approximating a low frequency component that is so low frequency, relative to the measurement window, that it appears to be constant.
I think in the case described here, the zero average amplitude thing has to do with something a little bit different.
Then how can the average amplitude be zero? If at any point the amplitude is nonzero, it must be positive (as it is the absolute value of the difference), thus the average can only be positive
IIRC the minimum is supposed to be 0.5 photons of any given wavelength. This is what gets called “zero point energy”.
Except there are ways to go below that, like a Casimir cavity.
I find these things confusing because when people explain Casimir cavities they never bother to say why the justification for zero point energy existing in the first place doesn’t apply within the cavity.
Indeed this is not possible for a classical wave. However, in a quantum description there exists a so-called "vacuum state" for which the expectation value of the electric field operator vanishes at all times, but the expectation value of the square of this operator does not. In the classical approximation of quantum optics, the expectation value of the electric field operator corresponds to the amplitude of the classical wave, whereas the expectation value of the square of the electric field operator corresponds to so-called shot (or quantum) noise on the classical wave.
Of course in nature there is no such thing as a "classical wave", so this description has to break down at some point. This is the case for vacuum fluctuations which simply do not have a classical explanation.
Exotic as the name seems, squeezed states are just Heisenberg’s uncertainty principle in action. In quantum optics, a light field is described by two “quadratures,” one for phase (P) and one for amplitude (X). Per Heisenberg, the minimum uncertainty of those two quadratures in a given measurement is given by the relation ΔXΔP = ħ/2. In other words, for a given measurement, the better you know the phase, the more potential error there is in the amplitude, and vice versa.
For a coherent state, such as a laser field, the phase and amplitude uncertainties are equal, giving rise to a circularly symmetric “fuzzball” of potential error between the two quadratures. But using nonlinear-optics techniques, the circle can be “squeezed” into an ellipse. That means that uncertainty in one quadrature—the one that’s relevant to your sensor—can be reduced, while the uncertainty in the other, less relevant quadrature are increased.
On quantum interferometer, I’ve always wondered if you could use it for navigation in space. Say you send a probe to another system. Navigating the uncharted system with precise gravity measurements that also expose its kinematics would be handy.
Physicist help needed: From my near null knowledge of quantum mechanics it seems they decrease randomness in phase and amplitude measurement by increasing uncertainty in mirrors position. So, this is interesting because the mirrors are macroscopic objects that interacted with the light in a rather simple way and conditions. On the other hand... Don't they require the mirror position in a well determined position to measure the gravitational waves?
They are increasing the precision of the phase while decreasing the precision of the amplitude. Since the amplitude of the light determines how hard it pushes on the mirrors, this has the side-effect of also making the positions of the mirrors more uncertain. To get the most accurate measurement possible, I'd guess that they would squeeze the light until getting any additional precision in the phase was not worth the added noise in mirror position.
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[ 3.5 ms ] story [ 68.0 ms ] threadI love this. Don't ask me what it means.
I think in the case described here, the zero average amplitude thing has to do with something a little bit different.
Except there are ways to go below that, like a Casimir cavity.
I find these things confusing because when people explain Casimir cavities they never bother to say why the justification for zero point energy existing in the first place doesn’t apply within the cavity.
Of course in nature there is no such thing as a "classical wave", so this description has to break down at some point. This is the case for vacuum fluctuations which simply do not have a classical explanation.
Heard of the Casimir effect? Two plates can experience a force from vacuum fluctuations.
Also works in other geometries, e.g., sphere and plate, two spheres, etc. First experimental verification was a sphere and a plate, I think? https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.78...
"...SQL is a direct consequence of the Heisenberg uncertainty principle..."