| Summary: | We study the current effectiveness of the dynamical decoupling technique on a publicly accessible IBM quantum computer (IBMQ). This technique, also known as bang-bang decoupling or dynamical symmetrization, consists of applying sequences of pulses for protecting a qubit from decoherence by symmetrizing the qubit–environment interactions. Works in the field have studied sequences with different symmetries and carried out tests on IBMQ devices typically considering single-qubit states. We show that the simplest universal sequences can be interesting for preserving two-qubit states on the IBMQ device. For this, we considered a collection of single-qubit and two-qubit states. The results indicate that a simple dynamical decoupling approach using available IBMQ pulses is not enough for protecting a general single-qubit state without further care. Nevertheless, the technique is beneficial for the Bell states. This encouraged us to study logical qubit encodings such as <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mfenced separators="" open="{" close="}"><msub><mrow><mo>|</mo><mn>0</mn><mo>⟩</mo></mrow><mi>L</mi></msub><mo>≡</mo><mo>|</mo><mn>01</mn><mo>⟩</mo><mo>,</mo><msub><mrow><mo>|</mo><mn>1</mn><mo>⟩</mo></mrow><mi>L</mi></msub><mo>≡</mo><mo>|</mo><mn>10</mn><mo>⟩</mo></mfenced></semantics></math></inline-formula>, where a quantum state has the form <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo>|</mo><msub><mi>ψ</mi><mrow><mi>a</mi><mi>b</mi></mrow></msub><mo>⟩</mo><mo>=</mo><mi>a</mi><msub><mrow><mo>|</mo><mn>0</mn><mo>⟩</mo></mrow><mi>L</mi></msub><mo>+</mo><mi>b</mi><msub><mrow><mo>|</mo><mn>1</mn><mo>⟩</mo></mrow><mi>L</mi></msub></mrow></semantics></math></inline-formula>. Thus, we explored the effectiveness of dynamical decoupling with a large set of two-qubit <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo>|</mo><msub><mi>ψ</mi><mrow><mi>a</mi><mi>b</mi></mrow></msub><mo>⟩</mo></mrow></semantics></math></inline-formula> states, where <i>a</i> and <i>b</i> are real amplitudes. With this, we also determined that the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo>|</mo><msub><mi>ψ</mi><mrow><mi>a</mi><mi>b</mi></mrow></msub><mo>⟩</mo></mrow></semantics></math></inline-formula> states most benefiting from this dynamical decoupling approach and slowed down the decay of their survival probability.
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