# Experimental optimal verification of entangled states using local measurements

July 24, 2020Quantum information is a field where the information is encoded into quantum states. Taking advantage of the "quantumness" of these states, we can perform more efficient computations and more secure cryptography compared to their classical counterparts.

A team led by Prof. GUO Guangcan from University of Science and Technology of China (USTC) of CAS modified the original proposal to be robust to practical imperfections, and experimentally implement a scalable quantum state verification on two-qubit and four-qubit entangled states with nonadaptive local measurements. The research results were published in

*Physical Review Letters*on July 17th.

The initialization of a quantum system into a certain state is a crucial aspect of quantum information science. While a variety of measurement strategies have been developed to characterize how well the system is initialized, for a given one, there is in general a trade-off between its efficiency and the accessible information of the quantum state. Conventional quantum state tomography can characterize unknown states while requiring exponentially expensive time-consuming postprocessing.

Alternatively, recent theoretical breakthroughs show that quantum state verification provides a technique to quantify the prepared state with significantly fewer samples, especially for multipartite entangled states.

In the research led by Prof. GUO Guangcan, for all the tested states, the estimated infidelity is inversely proportional to the number of samples, which illustrates the power to characterize a quantum state with a small number of samples. Compared to the globally optimal strategy which requires nonlocal measurements, the efficiency in their experiment is only worse by a small constant factor (<2.5).

They compared the performance difference between quantum state verification and quantum state tomography in an experiment to characterize a four-photon Greenberger-Horne-Zeilinger state, and the results indicate the advantage of quantum state verification in both the achieved efficiency and precision.

They experimentally realized an optimal quantum state verification (QSV), which is easy to implement and robust to realistic imperfections. The exhibited 1/n scaling results from the strategy itself without entangled or adaptive measurements.

Their results have clear implications for many quantum measurement tasks and may be used as a firm basis for subsequent work on more complex quantum systems.

-end-

University of Science and Technology of China

## Related Quantum Information Articles from Brightsurf:

Direct visualization of quantum dots reveals shape of quantum wave function

Trapping and controlling electrons in bilayer graphene quantum dots yields a promising platform for quantum information technologies.

Researchers discover a uniquely quantum effect in erasing information

Researchers from Trinity College Dublin have discovered a uniquely quantum effect in erasing information that may have significant implications for the design of quantum computing chips.

Avoiding environmental losses in quantum information systems

New research published in EPJ D has revealed how robust initial states can be prepared in quantum information systems, minimising any unwanted transitions which lead to losses in quantum information.

New technology lets quantum bits hold information for 10,000 times longer than previous record

Quantum bits, or qubits, can hold quantum information much longer now thanks to efforts by an international research team.

Simulating quantum 'time travel' disproves butterfly effect in quantum realm

Using a quantum computer to simulate time travel, researchers have demonstrated that, in the quantum realm, there is no 'butterfly effect.' In the research, information--qubits, or quantum bits--'time travel' into the simulated past.

Streamlining quantum information transmission

The Internet has deeply changed our ways of living but at the same time introduced serious security and privacy issues.

Orbital engineering of quantum confinement in high-Al-content AlGaN quantum well

Recently, professor Kang's group focus on the limitation of quantum confine band offset model, the hole states delocalization in high-Al-content AlGaN quantum well are understood in terms of orbital intercoupling.

AI enables efficiencies in quantum information processing

A new machine learning framework could pave the way for small, mobile quantum networks.

Quantum leap: Photon discovery is a major step toward at-scale quantum technologies

A team of physicists at the University of Bristol has developed the first integrated photon source with the potential to deliver large-scale quantum photonics.

Future information technologies: 3D quantum spin liquid revealed

Quantum Spin Liquids are candidates for potential use in future information technologies.

Read More: Quantum Information News and Quantum Information Current Events

Trapping and controlling electrons in bilayer graphene quantum dots yields a promising platform for quantum information technologies.

Researchers discover a uniquely quantum effect in erasing information

Researchers from Trinity College Dublin have discovered a uniquely quantum effect in erasing information that may have significant implications for the design of quantum computing chips.

Avoiding environmental losses in quantum information systems

New research published in EPJ D has revealed how robust initial states can be prepared in quantum information systems, minimising any unwanted transitions which lead to losses in quantum information.

New technology lets quantum bits hold information for 10,000 times longer than previous record

Quantum bits, or qubits, can hold quantum information much longer now thanks to efforts by an international research team.

Simulating quantum 'time travel' disproves butterfly effect in quantum realm

Using a quantum computer to simulate time travel, researchers have demonstrated that, in the quantum realm, there is no 'butterfly effect.' In the research, information--qubits, or quantum bits--'time travel' into the simulated past.

Streamlining quantum information transmission

The Internet has deeply changed our ways of living but at the same time introduced serious security and privacy issues.

Orbital engineering of quantum confinement in high-Al-content AlGaN quantum well

Recently, professor Kang's group focus on the limitation of quantum confine band offset model, the hole states delocalization in high-Al-content AlGaN quantum well are understood in terms of orbital intercoupling.

AI enables efficiencies in quantum information processing

A new machine learning framework could pave the way for small, mobile quantum networks.

Quantum leap: Photon discovery is a major step toward at-scale quantum technologies

A team of physicists at the University of Bristol has developed the first integrated photon source with the potential to deliver large-scale quantum photonics.

Future information technologies: 3D quantum spin liquid revealed

Quantum Spin Liquids are candidates for potential use in future information technologies.

Read More: Quantum Information News and Quantum Information Current Events

Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.