"qualitative shift" is correct and usable in written English.
You can use it to describe an improvement or transformation in the quality of something: The new sales team made a qualitative shift in customer service.
There has been a qualitative shift, too.
This is a qualitative shift in values and objectives.
That has led to a qualitative shift in the nature of the international system.
In other instances, nurses might simply notice a qualitative shift in the patient's appearance, cognitive ability, or demeanor.
"It's the beginning of a transition, a turning point and a qualitative shift in the political culture," said a legislator, Hanan Ashrawi.
This is a qualitative shift from earlier forms of censorship, in which students and faculty carefully danced around off-limits topics.
Now an investigation by the UN Monitoring Group on Somalia and Eritrea suggests that the plot was genuine, and says it represented "a qualitative shift in Eritrean tactics" in the Horn of Africa.
"In retrospect these were the kind of moments where there was a qualitative shift in the direction of society," he argues.
"The EU has moved from the level of statements, declarations and denunciations to effective policy decisions and concrete steps, which constitute a qualitative shift that will have a positive impact on the chances of peace," she said.
But we also want to see a qualitative shift in how institutions are run: they should be democratically governed public services, run by students and staff, and they should be places in which international students are welcomed, not exploited and surveilled.
The bombing and the clashes preceding it represent a qualitative shift in the ongoing war between the security services and Islamic militants believed to be either directly connected to Osama bin Laden and Al Qaeda or inspired by the terrorist group, Saudi officials and other analysts said.
