# Weekly Papers on Quantum Foundations (13)

On the Birth of the Universe and Time. (arXiv:2203.12984v1 [gr-qc])

A theory of the initial state of the universe is proposed within the framework of the Euclidean quantum theory of gravity. The theory is based on a quantum representation in which the action functional is implemented as an operator on the space of wave functionals depending on the 4D space metric and matter fields. The initial construction object is the eigenvalue of the action operator in the area of the Origin of the universe with the given values of the 3D metric and matter fields on the boundary. The wave function of the initial state is plotted as an exponential of this eigenvalue, after a Wick rotation in the complex plane of the radial variable of the Euclidean 4D space. An estimate of the initial radius of the universe is proposed.

Self-testing nonlocality without entanglement. (arXiv:2203.13171v1 [quant-ph])

Quantum theory allows for nonlocality without entanglement. Notably, there exist bipartite quantum measurements consisting of only product eigenstates, yet they cannot be implemented via local quantum operations and classical communication. In the present work, we show that a measurement exhibiting nonlocality without entanglement can be certified in a device-independent manner. Specifically, we consider a simple quantum network and construct a self-testing procedure. This result also demonstrates that genuine network quantum nonlocality can be obtained using only non-entangled measurements. From a more general perspective, our work establishes a connection between the effect of nonlocality without entanglement and the area of Bell nonlocality.

Effect of relativity and vacuum fluctuations on quantum measurement. (arXiv:2203.13187v1 [quant-ph])

Vacuum fluctuations can obscure the detection signal of the measurement of the smallest quantum objects like single particles seemingly implying a fundamental limit to measurement accuracy. However, as we show relativistic invariance implies the disappearance of fluctuations for the space-like %frequency-wavevector spectrum of an observable at zero temperature. This complete absence of noise can be harnessed to perform noiseless measurement of single particles, as we illustrate for electrons or photons. We outline a general scheme to illustrate the noiseless measurement involving the space-like spectrum of observables based on the self-interference of counter-propagating paths of a single particle in a triangular Sagnac interferometer.

Gravitational distortion on photon state at the vicinity of the Earth. (arXiv:2110.13990v2 [gr-qc] UPDATED)

As a photon propagates along a null geodesic, the space-time curvature around the geodesic distorts its wave function. We utilise the Fermi coordinates adapted to a general null geodesic, and derive the equation for interaction between the Riemann tensor and the photon wave function. The equation is solved by being mapped to a time-dependent Schr\”odinger equation in $(2+1)$ dimensions. The results show that as a Gaussian time-bin wavepacket with a narrow bandwidth travels over a null geodesic, it gains an extra phase that is a function of the Riemann tensor evaluated and integrated over the propagation trajectory. This extra phase is calculated for communication between satellites around the Earth, and is shown to be measurable by current technology.

Why the mean anomaly at epoch is not used in tests of non-Newtonian gravity?. (arXiv:2203.12951v1 [gr-qc])

Authors: Lorenzo Iorio

The mean anomaly at epoch $\eta$ is one of the standard six Keplerian orbital elements in terms of which the motion of the two-body problem is parameterized. Along with the argument of pericenter $\omega$, $\eta$ experiences long-term rates of change induced, among other things, by general relativity and several modified models of gravity. Thus, in principle, it may be fruitfully adopted together with $\omega$ in several tests of post-Newtonian gravity performed with astronomical and astrophysical binary systems. This would allow to enhance the gravitational signature one is interested in and to disentangle some competing disturbing effects acting as sources of systematic bias. Nonetheless, for some reasons unknown to the present author, $\eta$ has never been used so far by astronomers in actual data reductions. This note aims to raise interest in the community about the possible practical use of such an orbital element or, at least, to induce experts in astronomical data processing to explicitly make clear if it is not possible to use $\eta$ for testing gravitational models and, in this case, why.

Varying physical constants and the lithium problem. (arXiv:2010.13628v3 [gr-qc] UPDATED)

Authors: Rajendra P. Gupta

We have used the recently published varying physical constants (VPC) approach to resolve the primordial lithium abundance problem. The value of the ratio of $7Li$ to hydrogen $7Li/H=1.400(\pm 0.023){\times}10^{-10}$ we have calculated using this approach is about four times lower than that estimated using the standard lambda cold dark matter (${\Lambda}$CDM) cosmological model, and is consistent with the most agreed observational value of $1.6(\pm 0.3){\times}10^{-10}$. In the VPC approach Einstein equations are modified to include the variation of the speed of light $c$, gravitational constant $G$ and cosmological constant ${\Lambda}$ using the Einstein-Hilbert action. Application of this approach to cosmology naturally leads to the variation of the Plank constant $\hbar$ and the Boltzmann constant $k_B$ as well. They approach fixed values at the scale factor $a\ll 1$: $c=c_0/e$, $G=G_0/e^3$, $\hbar=\hbar_0/e$ and $k_B=k_{B0}/e^{5/4}$, where $e$ is the Euler’s number (=2.7183). Since the VPC cosmology reduces to the same form as the ${\Lambda}$CDM cosmology at very small scale factors, we could use an existing Big-Bang nucleosynthesis (BBN) code AlterBBN with the above changes to calculate the light element abundances under the VPC cosmology. Among other abundances we have calculated at baryon to photon ratio ${\eta}=6.1{\times}10^{-10}$ are: $4He/H =0.2478 (\pm 0.041)$, $D/H =2.453(\pm 0.041){\times}10^{-5}$ and $3 He/H=2.940(\pm 0.049){\times}10^{-5}$.

Pancosmic Relativity and Nature’s Hierarchies. (arXiv:2202.08860v2 [hep-th] UPDATED)

Authors: Nemanja Kaloper

We define `third derivative’ General Relativity, by promoting the integration measure in Einstein-Hilbert action to be an arbitrary $4$-form field strength. We project out its local fluctuations by coupling it to another $4$-form field strength. This ensures that the gravitational sector contains only the usual massless helicity-2 propagating modes. Adding the charges to these $4$-forms allows for discrete variations of the coupling parameters of conventional General Relativity: $G_N, \Lambda, H_0$, and even $\langle {\tt Higgs }\rangle$ are all variables which can change by jumps. Hence de Sitter is unstable to membrane nucleation. Using this instability we explain how the cosmological constant problem can be solved. The scenario utilizes the idea behind the irrational axion, but instead of an axion it requires one more $4$-form field strength and corresponding charged membranes. When the membrane charges satisfy the constraint $\frac{2\kappa_{\tt eff}^2 \kappa^2 |{\cal Q}_i|}{3{\cal T}^2_i} < 1$, the theory which ensues exponentially favors a huge hierarchy $\Lambda/\mpl^4 \ll 1$ instead of $\Lambda/\mpl^4 \simeq 1$. The discharges produce the distribution of the values of $\Lambda$ described by the saddle point approximation of the Euclidean path integral.

Decoupling Topological Explanations from Mechanisms

Kostic, Daniel and Khalifa, Kareem (2022) Decoupling Topological Explanations from Mechanisms. [Preprint]

Kaila’s interpretation of Einstein-Minkowski invariance theory

Slavov, Matias (2022) Kaila’s interpretation of Einstein-Minkowski invariance theory. Studies in History and Philosophy of Science, 93. pp. 57-65. ISSN 00393681

Information is Physical: Cross-Perspective Links in Relational Quantum Mechanics

Adlam, Emily and ROVELLI, Carlo (2022) Information is Physical: Cross-Perspective Links in Relational Quantum Mechanics. [Preprint]

Troubles with mathematical contents

Facchin, Marco (2021) Troubles with mathematical contents. [Preprint]

Can there be a process without time? Processualism within timeless physics

Margoni, Emilia (2022) Can there be a process without time? Processualism within timeless physics. [Preprint]

Renormalization Group Methods: What Explanation?

Castellani, Elena and Margoni, Emilia (2022) Renormalization Group Methods: What Explanation? [Preprint]

Calibrating the Universe: the Beginning and End of the Hubble Wars

Guralp, Genco (2020) Calibrating the Universe: the Beginning and End of the Hubble Wars. [Preprint]

A spotlight on circular states

Nature Physics, Published online: 24 March 2022; doi:10.1038/s41567-022-01572-5

Circular Rydberg states provide an ideal resource for large-scale quantum computing and simulation. These circular states can be controlled using coherent optical pulses, providing a route to programmable quantum hardware.

Simulation of open quantum systems by automated compression of arbitrary environments

Nature Physics, Published online: 24 March 2022; doi:10.1038/s41567-022-01544-9

It is difficult to analyse open quantum systems because an accurate description of their environments becomes intractably large. A method that automatically identifies an efficient representation provides a flexible approach to numerical simulations.

Collision detection with logic

Nature Physics, Published online: 21 March 2022; doi:10.1038/s41567-022-01550-x

Controlling chemistry at the single-collision level is one of the main goals of experiments at ultralow temperatures. A method based on quantum logic techniques has now been shown to detect inelastic collisions in a hybrid ion–atom platform.

Quantum logic detection of collisions between single atom–ion pairs

Nature Physics, Published online: 21 March 2022; doi:10.1038/s41567-022-01517-y

The study of single-atom collisions in ultracold gases has so far been limited to certain atomic and molecular species. A more general scheme based on quantum logic techniques has now been realized in a hybrid cold ion–atom platform.

Discrete symmetry breaking defines the Mott quartic fixed point

Nature Physics, Published online: 21 March 2022; doi:10.1038/s41567-022-01529-8

The Mott metal-to-insulator transition plays a key role in theoretical studies of high-temperature superconductors. A mathematical analysis of the theory of metals identifies a renormalization-group fixed point describing Mott physics.

Coordinates, Structure, and Classical Mechanics: A review of Jill North’s Physics, Structure, and Reality

Barrett, Thomas William (2022) Coordinates, Structure, and Classical Mechanics: A review of Jill North’s Physics, Structure, and Reality. [Preprint]