Related Experiment Video
Updated: Dec 9, 2025
09:23
Quantum State Engineering of Light with Continuous-wave Optical Parametric Oscillators
Published on: May 30, 2014
14.9K
Experimental Characterization of Unsharp Qubit Observables and Sequential Measurement Incompatibility via Quantum
Hammad Anwer1, Sadiq Muhammad1, Walid Cherifi1
1Department of Physics, Stockholm University, S-10691 Stockholm, Sweden.
Physical Review Letters
|September 10, 2020
Summary
This study demonstrates unsharp qubit measurements in a quantum random access code, outperforming classical and projective quantum methods. This advance enables noise-robust characterization and quantifies measurement incompatibility.
Area of Science:
- Quantum Information Science
- Quantum Foundations
- Quantum Measurement Theory
Background:
- Unsharp measurements are crucial for advancing quantum theory and quantum information applications.
- Implementing and characterizing these measurements is essential for practical quantum technologies.
Purpose of the Study:
- To experimentally implement unsharp qubit measurements within a sequential quantum random access code (QRAC).
- To demonstrate a nearly optimal sequential QRAC that surpasses classical and projective quantum protocols.
- To develop a noise-robust characterization of unsharp measurements and quantify measurement incompatibility.
Main Methods:
- Utilized a three-party sequential communication protocol involving qubit preparation, operation with classical/quantum outcomes, and measurement.
- Implemented unsharp qubit measurements in a quantum random access code framework.
- Applied noise-robust characterization techniques based on the sequential QRAC.
Main Results:
- Demonstrated a nearly optimal sequential quantum random access code.
- The implemented protocol outperformed the best classical and projective quantum protocols.
- Successfully achieved noise-robust characterization of unsharp measurements.
- Quantified the degree of incompatibility between sequential quantum measurement pairs.
Conclusions:
- Unsharp qubit measurements can be effectively implemented in sequential QRAC protocols.
- This approach offers advantages over classical and projective measurement-based quantum communication.
- The developed characterization method is robust to noise and useful for analyzing quantum measurement properties.
Related Concept Videos
00:59Propagation of Uncertainty from Random Error
1.5K
An experiment often consists of more than a single step. In this case, measurements at each step give rise to uncertainty. Because the measurements occur in successive steps, the uncertainty in one step necessarily contributes to that in the subsequent step. As we perform statistical analysis on these types of experiments, we must learn to account for the propagation of uncertainty from one step to the next. The propagation of uncertainty depends on the type of arithmetic operation performed on...
1.5K
02:46Uncertainty in Measurement: Reading Instruments
49.4K
Counting is the type of measurement that is free from uncertainty, provided the number of objects being counted does not change during the process. Such measurements result in exact numbers. By counting the eggs in a carton, for instance, one can determine exactly how many eggs are there in the carton. Similarly, the numbers of defined quantities are also exact. For example, 1 foot is exactly 12 inches, 1 inch is exactly 2.54 centimeters, and 1 gram is exactly 0.001 kilograms. Quantities...
49.4K
01:10Propagation of Uncertainty from Systematic Error
1.2K
The atomic mass of an element varies due to the relative ratio of its isotopes. A sample's relative proportion of oxygen isotopes influences its average atomic mass. For instance, if we were to measure the atomic mass of oxygen from a sample, the mass would be a weighted average of the isotopic masses of oxygen in that sample. Since a single sample is not likely to perfectly reflect the true atomic mass of oxygen for all the molecules of oxygen on Earth, the mass we obtain from this...
1.2K
02:45The Quantum-Mechanical Model of an Atom
55.7K
Shortly after de Broglie published his ideas that the electron in a hydrogen atom could be better thought of as being a circular standing wave instead of a particle moving in quantized circular orbits, Erwin Schrödinger extended de Broglie’s work by deriving what is now known as the Schrödinger equation. When Schrödinger applied his equation to hydrogen-like atoms, he was able to reproduce Bohr’s expression for the energy and, thus, the Rydberg formula governing hydrogen spectra.
55.7K
03:37Uncertainty in Measurement: Accuracy and Precision
98.8K
Scientists typically make repeated measurements of a quantity to ensure the quality of their findings and to evaluate both the precision and the accuracy of their results. Measurements are said to be precise if they yield very similar results when repeated in the same manner. A measurement is considered accurate if it yields a result that is very close to the true or the accepted value. Precise values agree with each other; accurate values agree with a true value.
98.8K
01:00Detection of Gross Error: The Q Test
6.7K
When one or more data points appear far from the rest of the data, there is a need to determine whether they are outliers and whether they should be eliminated from the data set to ensure an accurate representation of the measured value. In many cases, outliers arise from gross errors (or human errors) and do not accurately reflect the underlying phenomenon. In some cases, however, these apparent outliers reflect true phenomenological differences. In these cases, we can use statistical methods...
6.7K