Summary: | In recent years, many works have explored possible advantages of <i>indefinite causal order,</i> with the main focus on its controlled implementation known as <i>quantum switch</i>. In this paper, we tackle advantages in quantum thermodynamics, studying whether quantum switch is capable of activating a passive state, either alone or with extra resources (active control state) and/or operations (measurement of the control system). By disproving the first possibility and confirming the second one, we show that quantum switch is not a thermodynamic resource in the discussed context, though it can facilitate work extraction given external resources. We discuss our findings by considering specific examples: a qubit system subject to rotations around the <i>x</i> and <i>y</i> axes in the Bloch sphere, as well as general unitaries from the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>U</mi><mo>(</mo><mn>2</mn><mo>)</mo></mrow></semantics></math></inline-formula> group; and the system as a quantum harmonic oscillator with displacement operators, as well as with a combination of displacement and squeeze operators.
|