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For electromagnetic waves there exists a wave/particle duality: light sometimes behaves as a wave, and other times as a particle (photons).

Does such a duality exist for gravitational waves? In other words would we expect gravitational waves to sometimes behave has particles (gravitons)?

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    $\begingroup$ The wave/particle duality is not a classical/quantum duality. It is a duality that exists solely in quantum theory. Hence photon themselves exhibit a wave/particle duality as do electrons. $\endgroup$ – Lewis Miller Feb 12 '16 at 16:38
  • $\begingroup$ Let me, again, say that wave-particle duality is an 80+ year old misconception. It's not valid for photons, or electrons or gravitons (if they exist, which I would question in the first place). $\endgroup$ – CuriousOne Feb 12 '16 at 20:14
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Yes. Gravitational waves have been observed, and assuming that quantum mechanics is the right way to think about the universe, then weak gravitational waves of the sort that can be observed at LIGO can be thought of as coherent ensembles of 'graviton' particles.

Now, theoretically this picture is 'OK' because although any quantum field theory that describes gravity is nonrenormalizable, the energy scale at which we expect new physics associated with gravity to be detectable is extremely large ($\sim 10^{19} \text{GeV}$). Hence, we can use an effective theory valid at low energies to describe gravity in terms of particles, even if the 'true' theory of gravity valid at arbitrary energies or length scales is somewhat different conceptually.

Unfortunately, it's impossible with current technology to observe or manipulate single gravitons in a lab, so gravitons are still theoretical.

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  • $\begingroup$ But considering we can now 'see' gravitational waves, and are looking to increase our ability to resolve with projects like LISA, might we be able to conceive and conduct experiments similar to Young's double slit experiment that doesn't depend on a few gravitons, and possibly work with an ensemble? I guess the problems are that wave events are far and few between, and its hard to imagine what might serve as slits for gravitational waves. Perhaps another experiment, approach in quantum mechanics needs to be considered - or invented. $\endgroup$ – docscience Feb 22 '16 at 0:42
  • $\begingroup$ What makes you think yes? There is no experimental evidence (for particle gravitons), neither is there a functioning theory. $\endgroup$ – lalala Mar 23 '18 at 13:12
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Although we lack the technology to observe gravitons, and our observation of gravitational waves is very recent and too early to absolutely confirm, gravitons should exist due to quantum theory which states that every elementary and undivisible particle does experience wave-particle duality.

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