Mar 7 2018

**Imagine there being a deeper reality - think of our universe as a mere illusion. Ever imagined all of us living in a hologram? **

Or, as an alternative, ask Matthew Headrick, associate professor of physics, about his study. Headrick deals with one of the most advanced theories in theoretical physics, that is, the holographic principle. It is well known that the universe is a three-dimensional image projected from a two-dimensional surface, very similar to a hologram emerging from a photographic film.

*In my view, the discovery of holographic entanglement and its generalizations has been one of the most exciting developments in theoretical physics in this century so far. **What other new concepts are waiting to be discovered, and what other unexpected connections? We can’t wait to find out*.

Matthew Headrick

From 2016, Headrick has worked as deputy director of the “*It from Qubit: Quantum Fields, Gravity and Information*” project, an international attempt by 18 researchers and their labs to ascertain if the holographic concept is precise. The New York-based Simons Foundation has funded the 4-year, $10-million grant.

If Headrick and his team could prove the holographic concept, they would have reached a significant step forward in accomplishing the holy grail of theoretical physics, a grand integrated theory with the ability to elucidate all the laws and concepts that govern reality. “*We’re not there yet*,” stated Headrick, “*but we’re making progress*.”

Below, the holographic concept has been broken down step by step.

**Information**

To start with, we will take smaller steps. For a much longer time, it has been considered that the universe at its most basic level is formed of subatomic particles such as quarks or electrons. However, at present, physicists consider that those particles are formed of something even minute, that is, information.

Talking about information, physicists refer to data that describe physical phenomena. An object’s mass, an electron’s spin direction, and e = mc^{2} are all units of information.

If one can collect all the information found out there, he or she would own the complete instruction booklet for constructing everything in the universe.

**Qubits**

The most infinitesimal levels of the universe are controlled by the quantum mechanical laws. At such levels, things begin to seem very strange and illogical.

In the world of quantum mechanics, units of information are termed qubits.

Headrick analyzes the quantum entanglement of qubits, a very weird phenomenon characteristic to the quantum mechanical world.

Consider having two qubits with values that can be either 1 or 0. Upon intertwining the qubits, their values get correlated. On evaluating the first qubit, its value might be 0. On checking the value of the other qubit, it might also be 0. However, consider that the value of the first qubit is 1. Here, the value of the second qubit could also change to 1.

It seems like the qubits communicate with one another, with the first intimating the second, “*Hey, this physicist over here just found out I’m a 1. You better be a 1, too*.” Strangely but strikingly, this communication can occur over extensive distances with messages apparently relayed quicker than the speed of light.

**Qubits are flat**

In the majority of cases, upon dropping an object (e.g., a jelly bean) into a jar, it falls inside and occupies space. When one or more jelly bean is added, there is a decrease in the amount of unfilled space and there is an increase in the volume of the jelly beans.

This does not work in the case of qubits. Qubits do not fall into the jar but, in contrast, spread out on a surface. When a qubit is added, it will stick to the jar’s side. Adding another qubit will also lead to the same consequence. If the number of qubits is increased, the volume is not increased. Rather, the surface area occupied by the qubits is increased.

The two-dimensional plane described by the holographic concept is achieved by adding more and more qubits that get spread out across a flat surface.

**Three Dimensions**

Moving beyond the infinitesimal realm, the quantum mechanical laws no longer hold good. As it sounds unusual, at the macrocosmic level, a distinctive set of physical laws are needed to explain the occurrences.

Consider Einstein’s theory of relativity. In order to compute cosmic events such as the orbit of Mercury around the sun or the path followed by light, the theory of relativity is very important.

Although the building blocks of relativity are also information units, at present they are termed bits.

The functionalities of bits are quite familiar to us. They occur in three dimensions.

**Holograms**

Consider again the two-dimensional surface occupied by entangled qubits. Due to the fact that the value of a qubit gets modified based on the value of its entangled pair, there is a specific level of uncertainty formed in the system. If one has not yet evaluated the first qubit, then the value of the second cannot be ascertained. The amount of indeterminacy in any given system is known as its entropy.

When qubits get entangled and disentangled, the level of entropy increases and decreases, respectively. One ends up finding fields of entropy in a continuously changing state.

The holographic concept proposes that our three-dimensional realm is a projection or representation of all the activity occurring on a two-dimensional surface covered with qubits.

**Putting it all together**

Physicists have always been worried about the fact that there is one set of rules for the microcosmic, quantum mechanics, and a different set for the macrocosmic, the theory of relativity. It would be meaningless to consider that there must be two distinctive and incongruent groups of mathematical formulas governing our universe. Physicists suggest that there ought to be some means to strike a harmony between the two.

Hence, here is the principal question for Headrick and his team: Beginning with the two-dimensional realm of qubits and quantum mechanics, and then moving up in size, how accurately can we wind up with relativity and bits? It relates to nothing but building a single mathematical model that throws light on the transformation.

By figuring this out, one can solve one of the huge mysteries in theoretical physics. From the infinitesimal to the largest phenomenon, we could have a consolidated theory of reality.

At present, the holographic concept is still unproven. To which point this might lead us is still unanswered. However, it might be weirder than anything yet visualized in science fiction.

Source: http://www.brandeis.edu/