Quantum Memory Reaches New Record

Quantum computers reaches new record

Quantum memory is known to be extremely fickle and difficult to manipulate and measure, but scientists have now been able to hold this fragile quantum memory state stable at room temperature for a new “world record” of 39 minutes.

Although no official quantum record has been set for solid states, the former best time was only three minutes in crycogenic conditions and 25 seconds at room temperature.

Quantum systems store “qubits” in a “superposition state.” Unlike conventional computers, that store “bits” of data in a sequence of ones and zeros, the “qubits”  stored in quantum computers can be one or zero simultaneously. This is what enables the quantum computer to accomplish several multiplications at the same time.

This brings the promise of ultra fast quantum computers one step closer to fulfillment. The findings have been published in the online Science Journal.

Once quantum memories are able to accumulate and retrieve intelligible information for a prolonged period of time, a new world of technological advancement will be available.

Using shallow neutral donors, scientist have been studying how electron and nuclear spin qubits in semiconductors. The studies have shown that these are restricted to extremely low temperatures.

However, scientists have now found that the nuclear spin of ionized donors could be effective in much higher temperatures.

Scientists programmed data into the nuclei of phosphorus atoms contained by decontaminated silicon. Tilting the nuclei’s spin using magnetic field impulses created the “qubits” of memory.

The study details how optical means and dynamical decoupling was applied in order to utilize the nuclear spin of ionized donors. The scientists placed phosphorous-31 donors in silicon that had been purified isotopically and observed the effects of the nuclear spin and phosphorous- 31 donors in room temperature over a period of 39 minutes, a new time record.

The scientists then went on to cycle a coherent spin superposition from 4.3 kelvin to room temperature, and back again. In this same system, the scientists found that a cryogenic coherence time of three hours could be attained.

According to the editor of the paper, using silicon for quantum materials streamlines the integration of such quantum materials with the electrical components already used by computers, making it easier to merge quantum computing and computers already in use.

However, solids have been found to have an affect on “qubits’” coherence times, especially in room temperature. In order to improve the length of coherence times the isotopic contamination of the host material, in this case the silicon, need to be removed. This is because the magnetic isotopes found in unpurified silicon interfere with a nuclei’s spin.

The scientists attempted this feat by using positively charged donors instead of neutral donors. This optical manipulation was done using dynamic decoupling.

It was this management of the host material that enabled the scientists to lengthen the “qubits’” coherence time to a new record of 39 minutes at a stable room temperature and three hours at cryogenic temperatures.  This new record for quantum memory is an exciting achievement because it has proven what many experts in the field have predicated, marking an entrance into a new era of computing.

Jessica Rosslee

Online Science Journal

BBC News

Live Science

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