«relating to exciton-polaritons, it is common to speak of quantum vortices, quantum fluids, or quantum something.»
The future of quantum in polariton systems: opinion. T. C. H. Liew in Opt. Mater. Express 13:1938 (2023). What the paper says!?
More than "an opinion", this is a review of the state of the art of quantum polaritonics (the Author himself states that «this is far from a complete review of the field».)
It provides, as such, a nice list of references, although very few comments are given on each work.
This measure of polariton interactions is given as:
This does not mean that polaritons are bad. Indeed, it was pointed out long ago that they typically require powers four orders of magnitude lower than other
photonic systems to show nonlinear transitions [18]
The cross-Kerr modulation has been measured around 3mrad per polariton [21], which is better than other photonic systems (although not at the level attained
with quantum dots or atomic emitters)
which it concludes with:
Ideally though, polaritons could reach deeper into the
quantum regime.
The unconventional blockade section is described as «Avoiding the conventional blockade» and the underlying physics is not really explained. In fact it is unclear if it is even understood. This, for instance, is not true:
A limitation of the unconventional blockade is that the antibunching only occurs in a narrow time window, due to the presence of an oscillation associated to the inter-mode coupling that
should be fast compared to the system decay rate.
Unconventional blockade arises from the interference of a coherent and a squeezed state. As those are typically detuned in frequency in actual (many, coincidental) implementations, this produces oscillations, but this is concomitant, not a requirement of the scheme.
The following is true but is not contrasted against schemes that do exactly this (such as Demirchyan[1]:
In the quantum case, when a polariton is lost from the system it takes with it all the correlations with the remaining particles, and this information can not be replaced
by adding a new polariton with the wrong correlations.
Instead, on this paper, he comments:
in the absence
of strong polariton blockade, it has been pointed out that we must appreciate that we do not have a fixed well-defined number of particles
There is a nice review of polariton neural networks, although, strangely, the Author does note cite his own pioneering work[2] but goes straight to later works, which is unclear why.
He cites some of our works, that are central to the theme as a whole, but those are hardly discussed, mainly mentioned (like most of the other papers). In particular, my paper Exciting Polaritons with Quantum Light,[3] which clearly is relevant to such an opinion or review, is not cited.
As a conclusion, the Author rightly observes that:
Even though quantum polaritonics represents a small fraction of the research in exciton-polaritons,
which overwhelmingly focuses on classical effects, there are enough papers to define an emerging field.
and makes a poetic conclusion:
The key milestones, such as quantum blockade, and niche applications have been
identified for the near-term. It is too soon to put a limit on the long-term.
References
- ↑ Qubits Based on Polariton Rabi Oscillators. S. S. Demirchyan, I. Yu. Chestnov, A. P. Alodjants, M. M. Glazov and A. V. Kavokin in Phys. Rev. Lett. 112:196403 (2014).
- ↑ Optical Circuits Based on Polariton Neurons in Semiconductor Microcavities. T. C. H. Liew, A. V. Kavokin and I. A. Shelykh in Phys. Rev. Lett. 101:016402 (2008).
- ↑ Exciting Polaritons with Quantum Light. J. C. López Carreño, C. Sánchez Muñoz, D. Sanvitto, E. del Valle and F.P. Laussy in Phys. Rev. Lett. 115:196402 (2015).