Lifeboat Foundation

Photonic qudits are emerging as an essential resource for environment-resilient quantum key distribution, quantum simulation and quantum imaging and metrology¹. The availability of unbounded photonic degrees of freedom, such as time-bins, temporal modes, orbital angular momentum (OAM) and radial number¹, allows for encoding large amounts of information in fewer photons than would be required by qubit-based protocols (for example, when using only polarization). At the same time, the large dimensionality of these states, such as those emerging from the generation of photon pairs, poses an intriguing challenge for what concerns their measurement. The number of projective measurements necessary for a full-state tomography scales quadratically with the dimensionality of the Hilbert space under consideration². This issue can be tackled with adaptive tomographic approaches^3,4,5 or compressive techniques^6,7, which are, however, constrained by a priori hypotheses on the quantum state under study. Moreover, quantum state tomography via projective measurement becomes challenging when the dimension of the quantum state is not a power of a prime number⁸. Here we try to tackle the tomographic challenge, in the specific contest of spatially correlated biphoton states, looking for an interferometric approach inspired by digital holography^9,10,11, familiar in classical optics. We show that the coincidence imaging of the superposition of two biphoton states, one unknown and one used as a reference state, allows retrieving the spatial distribution of phase and amplitude of the unknown biphoton wavefunction. Coincidence imaging can be achieved with modern electron-multiplying charged coupled device cameras^12,13, single photon avalanche diode arrays^14,15,16 or time-stamping cameras^17,18. These technologies are commonly exploited in quantum imaging, such as ghost imaging experiments¹⁹ or quantum super-resolution^20,21, as well as for fundamental applications, including characterizing two-photon correlations^13,22, imaging of high-dimensional Hong–Ou–Mandel interference^23,24,25, and visualization of the violation of Bell inequalities²⁶. Holography techniques have been recently proposed in the context of quantum imaging^27,28,29; demonstrating the phase-shifting digital holography in a coincidence imaging regime using polarization entanglement²⁷, and exploiting induced coherence, that is, the reconstruction of phase objects through digital holography of undetected photons²⁸.

In this work, we focus on the specific problem of reconstructing the quantum state (in the transverse coordinate basis) of two photons emerging from degenerate spontaneous parametric down-conversion (SPDC). These states are characterized by strong correlations in the transverse position (considered on the plane where the two-photon generation happens), which can be observed in other kinds of photon sources such as cold atoms³⁰. In these sources, the two-photon wavefunction strongly depends on the shape of the pump laser used to induce the down-conversion process³¹. The most commonly used approach in the literature to reconstruct the biphoton state emitted by a nonlinear crystal is based on projective techniques^32,33,34. This method has drawbacks concerning measurement times (as it needs successive measurements on non-orthogonal bases) and the signal loss due to diffraction. We proposed an imaging-based procedure capable of overcoming both of the issues mentioned above, while giving the full-state reconstruction of the unknown state. The core idea lies in assuming the SPDC state induced by a plane wave as known, and in superimposing this state with the unknown biphoton state. Unless the superposition is achieved directly on the crystal plane, a full analysis of the four-dimensional distribution of coincidences is necessary to retrieve the interference between the two wavefunctions. This information can be visualized by observing coincidence images, defined as marginals of the coincidence distribution obtained integrating over the coordinates of one of the two photons. In fact, obtaining coincidence images after post-selecting specific spatial correlations allows retrieval of the phase information, likewise in cases in which the state does not exhibit sharp spatial correlations. We demonstrate this technique for pump beams in different spatial modes, including Laguerre–Gaussian (LG) and Hermite–Gaussian (HG) modes. We investigate several physical effects from the reconstructed states, such as OAM conservation, the generation of high-dimensional Bell states, parity conservation and radial correlations. Remarkably, we show how, from a simple measurement, one can retrieve information about two-photon states in arbitrary spatial mode bases without the efficiency and alignment issues that affect previously implemented projective characterization techniques. Depending on the source brightness and the required number of detection events, the measurement time can be of the order of tens of seconds, whereas the previously implemented projective techniques required several hours and were limited to the exploration of a small subspace of spatial modes. As a latter example, we give a proof of principle demonstration of the use of this technique for quantum imaging applications.

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A type 5 civilization often seen as unattainable is actually quite possible. We could have computers to use a developer mode to solve all sorts of problems like the entropy of the universe and even stop the entropy of the earth or stop meteorites from hitting earth with a computer click. This could easily be attainable with technological singularities leading to a new understanding of our universe but should be considered to essentially stop almost any problem to earth and beyond.

Type 1 civilization designation on the Kardashev scale may be possible in the next 100 years, which could influence the survival of mankind.

Simulations utilizing ‘modest computational systems’ have achieved equivalent results as the technology multinational, just weeks after the milestone was published in the journal ‘Nature’

An electromechanical device allows researchers to control and study how a nanoscale beam buckles when compressed.

The buckling of a column or other structural element is typically something that engineers want to avoid, but a new device offers a way to control this type of deformation on microscopic scales. The design combines small actuators and circuits that generate mechanical and electrostatic forces on a nanoscale beam, causing it to buckle to the left or to the right. By manipulating the beam’s deformation, researchers may be able to harness buckling for sensitive detectors or for testing the relationship between thermodynamics and computing.

To improve access to large data sets, scientists are looking to cloud-based solutions for data management.

In the coming decade, big projects like the Large Hadron Collider (LHC) and the Square Kilometre Array (SKA) are each expected to produce an exabyte of data yearly, which is about 20 times the digital content of all the written works throughout human history. This information overload requires new thinking about data management, which is why scientists have begun to look to the “cloud.” In such a scenario, data would be stored and analyzed remotely, with the advantage that information would become more accessible to a wider scientific community. Efforts are underway to create “science clouds,” but disagreements remain over their structure and implementation. To discuss these details, around 60 scientists came together for The Science Cloud meeting in Bad Honnef, Germany. The attendees shared lessons from past and ongoing projects in the hope of building the groundwork for a future scientific computing infrastructure.

In the ’80s, the spy agency investigated the “Gateway Experience” technique to alter consciousness and ultimately escape spacetime. Here is everything you need to know.

She turned to me the other morning and said, “You heard of The Gateway?” It didn’t register in the moment. She continued, “It’s blowing up on TikTok.” Later on, she elaborated: It was not in fact the ill-fated ’90s computer hardware company folks were freaking out about. No, they’ve gone further back in time, to find a true treasure of functional media.

The intrigue revolves around a classified 1983 CIA report on a technique called the Gateway Experience, which is a training system designed to focus brainwave output to alter consciousness and ultimately escape the restrictions of time and space. The CIA was interested in all sorts of psychic research at the time, including the theory and applications of remote viewing, which is when someone views real events with only the power of their mind. The documents have since been declassified and are available to view.

Continue reading “How to Escape the Confines of Time and Space According to the CIA” »

For nearly 40 years, materials called ‘strange metals’ have flummoxed quantum physicists, defying explanation by operating outside the normal rules of electricity.

Now research led by Aavishkar Patel of the Flatiron Institute’s Center for Computational Quantum Physics (CCQ) in New York City has identified, at long last, a mechanism that explains the characteristic properties of strange metals.

In the August 18 issue of Science, Patel and his colleagues present their universal theory of why strange metals are so weird—a solution to one of the greatest unsolved problems in condensed matter physics.

Dr. Michio Kaku, the renowned theoretical physicist, walks us through the evolutionary journey of computing, from analog to digital to the quantum era.

Quantum computers hold immense promise because of their ability to tap into the weirdness of quantum mechanics. If nature allows us full access to its secrets, we could boost computing power exponentially, which in turn would allow us to solve all types of complex problems.