New Phase of Matter Opens Portal to Extra Time Dimension

The ancient Incas used a device called a quipu to store their tax and census records. Physicists are on their way to developing a modern equivalent of hundreds of years ago. Theirquipu is a new phase of matter created within a quantum computer and their strings are atoms.

It is not as incomprehensible as it appears. The new phase is part of a family of phases that were first identified in the 1980's. The order of the materials is not determined by how they are arranged, but by how they move and interact. A new phase of matter can be created by applying new combinations of fields and lasers. The symmetries can be found in time instead of space. A two-dimensional hologram is a lower-dimensional projection of a three-dimensional object. It is possible to discern the symmetries of this newly created phase by looking at it in two time dimensions.

The mathematical description of the phase of matter is based on a theoretical extra time dimensions, which is very exciting to see in an experiment. The paper was published in Nature.

The physicists' original plan was not to open a portal to an extra timeDIMENSION. Andrew Potter is a quantum physicist at the University of British Columbia. After imagining their new phase, the team members realized it could help protect data being processed in quantum computers.

The predicted power of quantum computers is derived from the ability of quantum bits, or qubits, to store values of either 0 or 1 at the same time. Most quantum computers store information in the state of each qubit, for instance in an internal quantum property of a particle, which can point up or down at the same time. Any noise, even a stray magnetic field, could wreak havoc on a carefully prepared system and even destroy quantum effects.

Potter says this vulnerability is similar to conveying a message using pieces of string, with each string arranged in the shape of an individual letter. He says you could read it until a small breeze blows it away. The more error-proof quantum material was created by Potter's team. Information is woven across the material around the world in a quantum computer. Potter says quipu is like a knot that is hard to untie.

The topological phases offer a way to protect against errors that are built into the material. Traditional error-correcting protocols involve measuring a small piece of the system to make sure there are no errors and then going in and fixing them.

The H1 quantum processor is composed of a strand of 10 qubits in a vacuum chamber with lasers controlling their positions and states. Physicists use a technique called an ion trap. In their first attempt to create a topological phase that would be stable against errors, Potter, Dumitrescu and their colleagues tried to make the processor with a simple time symmetry by giving periodic kicks to the ion. Potter says that back-of-the-envelope calculations suggest this would protect the quantum processor. A steady drumbeat can keep a lot of dancers in motion.

The researchers ran the program multiple times on the processor to make sure the quantum state of all the qubits was in line with their predictions. Potter jokes that it didn't work at all. It was incomprehensible. The system's performance was degraded by 1.5 seconds every time. It wasn't enough to just add one time symmetry. Potter explains that the periodic laser pulse were making small disruptions worse, rather than preventing the qubits from being affected by knocks and noise.

He and his colleagues went back to the drawing board and came up with an idea: if they could create a pattern ofpulses that were ordered and not random, they could create a more resilient phase. The pattern could potentially cause multiple symmetries in the processor's ytterbium qubits while avoiding the unwanted amplifications. The next number in the sequence is the sum of the previous two, which is a well-known pattern in mathematics. A periodic laser pulse sequence that alternates between two frequencies from two lasers would be called A, B, A, B...

Potter says that the system can be considered as two lasers pulse with two different frequencies that ensure that the pulse never overlaps. For the purpose of its calculations, the theoretical side of the team imagined these two independent collections of beats, each with its own time line. The surface of a torus contains two time dimensions. Potter says that the quasi-periodic nature of the dual time lines can be seen by how they wrap around the torus again and again.

The team implemented a new program with a quasi-periodic sequence that protected the processor for the full length of the test. It doesn't sound like much, but it is. The demonstration is working.

An expert on quantum computing at the University of California, Santa Barbara was not involved in the study. Two-dimensional spatial systems offer better protection against errors than one-dimensional systems, but they are more expensive to build. This limitation is circumvented by the second time dimensions created by the team. The one-dimensional system acts like a higher-dimensional system without the overhead of making a two-dimensional system. It is the best of both worlds because you can have your cake and eat it as well.

Samuli Autti is a quantum physicist at Lancaster University in England who was not involved with the team. Less active control methods have made quantum computers more static and less flexible. Autti says that dynamic protection is a major goal.

The researchers assigned to the new phase of matter have a mouthful of a name, but it's recognition of its potential is what makes it worthwhile. Potter would like to think of a better name.

The original failed test revealed that the quantum computer was more error prone than thought. It was a good way of testing how good the processor is.